12.12.22 TAB Agenda 4 VZIP Evaluation and Next StepsCITY OF BOULDER
TRANSPORTATION ADVISORY BOARD
AGENDA ITEM
MEETING DATE: December 12, 2022
AGENDA TITLE: Public hearing and consideration of a recommendation to City Council on
Evaluation and Next Steps for the Vision Zero Innovation Program (VZIP)
PRESENTER(S):
Natalie Stiffler, Interim Director of Transportation and Mobility
Devin Joslin, Principal Traffic Engineer
Melanie Sloan, Transportation Principal Project Manager
EXECUTIVE SUMMARY
This memo provides an overview of the Vision Zero Innovation Program (VZIP) and the methodology
used to evaluate the effectiveness of projects installed in 2020 and 2021. The VZIP was initiated in 2020
through a one-time funding allocation from City Council to Transportation & Mobility to advance
progress toward Vision Zero. The purpose of the VZIP is primarily to support traffic calming and
pedestrian crossing projects and serve to evaluate the effectiveness of various low-cost, quick-build
projects comprised of primarily paint, flexible delineator posts, and/or rubberized curbs/concrete wheel
stops. The projects generally fall into one of three categories: curb extensions, crossing treatments
(pedestrian refuge islands and hardened centerlines) and traffic calming (pinch points and chicanes).
These projects offer low-cost solutions aimed at mitigating speed-related crashes and crashes involving
vulnerable roadway users by increasing corner clearances, shortening crossing distances, and slowing
vehicle speeds for both turning and through traffic. The installation locations were identified through
various studies/programs and community input.
Throughout the duration of the VZIP, staff have provided TAB with updates at key decision points,
including August 2020, March 2021, and July 2021. In particular, TAB provided staff with feedback on
the proposed inclusion of NSMP Complex Corridors into the program, as well as the approach to project
identification and selection. In 2022, staff has been completing an evaluation study focused on assessing
the effectiveness of installed VZIP projects using quantitative and qualitative criteria to develop
proposed recommendations for projects based on results of the evaluation. Consistent with the ongoing
community-based processes inherent to the VZIP to date, a public hearing is being held as part of this
agenda item to provide community members the opportunity to comment on the proposed
recommendations and allow TAB members to consider community feedback prior to considering a
motion to support the proposed recommendations resulting from the VZIP evaluation study. Final
changes to approved VZIP projects will be made in early- to mid-2023.
The purpose of this agenda item is to share the draft VZIP evaluation report, summarize community
feedback, share the proposed project recommendations, and consider the comments received during the
public hearing to receive a recommendation from TAB on the evaluation study and next steps.
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BACKGROUND OF THE VISION ZERO INNOVATION PROGRAM (VZIP)
The VZIP was initiated as part of Boulder’s Vision Zero goal of eliminating fatal and serious injury
crashes. The program delivered quick-build, cost-effective, innovative, and community-responsive
projects to reduce vehicle speeds and improve bicycle and pedestrian crossing comfort on the city’s
residential streets. The program was able to deliver projects at 20 spot locations and along five
residential street corridors within a constrained budget in approximately 14 months (August 2020-
October 2021).
The VZIP project locations were identified either through safety analyses, such as the Safe Streets
Report, 3rd Edition, 2019, sourced from Neighborhood Speed Management Program (NSMP)
community-driven petitions, BeHeardBoulder questionnaire responses, feedback from the Pedestrian
Action Committee and regional Vision Zero Community Partnership stakeholders or via other
community engagement efforts such as direct communication between community members and staff.
VZIP projects were installed in 20 spot locations throughout the city and along five residential street
corridors: Quince Avenue, Palo Parkway, Glenwood Drive, Aurora Avenue, and Mohawk Drive.
Attachment A illustrates the location of VZIP projects installed across the city in 2020 and 2021.
The program primarily installed horizontal deflection treatments, which either visually narrow the
roadway using paint and devices, like flexible delineators, or cause drivers to change their travel path to
navigate around devices. Temporary vertical deflection treatments, such as speed humps, were not part
of VZIP because of their incompatibility with snow removal.
VZIP EVALUATION PURPOSE AND METHODOLOGY
The purpose of the evaluation study is to evaluate the effectiveness of treatments installed in 2020 and
2021 to recommend where to keep, modify, or remove treatments using both objective and subjective
evaluation criteria. The criteria assessed the extent to which installed projects reduced speeds; improved
pedestrian and bicyclist crossing comfort; impacted emergency response, snow/ice removal, and street
sweeping; and required ongoing maintenance, such as replacement of damaged delineators.
Attachment B is a copy of the draft evaluation study report. The report provides comprehensive
information related to the evaluation methodology, recorded data summaries, community feedback
received, and makes recommendation on whether to keep, modify or remove each treatment.
The recommendations were based on three evaluation categories: speed reduction, crossing comfort, and
maintenance. The type of data collected for each category depended on the purpose for installing the
treatment (e.g., traffic calming, slower turning speeds, crossing comfort) and the treatment type, The
goal of each category evaluation is to determine whether the treatment achieved the desired outcome(s).
If a treatment whose primary purpose was not met based on the evaluation, the treatment is
recommended to be removed.
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Speed reduction was assessed using before and after data collected at each project site. Data recorded
average speeds; 50th, 85th, and 95th percentile speeds; the number of speeding vehicles traveling greater
than 5 miles-per-hour (mph) over the posted speed limit; the number of speeding vehicles traveling
greater than 10 mph over the posted speed limit; average daily traffic volumes; and additional, modal-
specific data such as pedestrian crossing counts.
Improving pedestrian and bicyclist crossing comfort was evaluated primarily through review of
community feedback that shared experience traveling through project sites before and after a treatment
was installed. Other factors considered in this category include if the treatment was located on a
Neighborhood GreenStreet or designated bike route, to what extent the treatment encourages careful
driving, and the extent to which public feedback expressed a desire for the treatment to be made
permanent.
Maintenance was evaluated using maintenance records for each treatment as well as feedback from the
city’s emergency response and maintenance divisions on the ease of navigating their vehicles through
and effectively performing maintenance duties within the project area.
COMMUNITY ENGAGEMENT SUMMARY
Community engagement has been an integral part of VZIP and was a component considered when
assessing the impact and success of installed VZIP projects. Though staff received VZIP project related
phone calls, emails, and tickets through Inquire Boulder (the city’s customer service portal), the majority
of VZIP feedback (over 300 comments) were submitted through a Formstack questionnaire on the
project webpage. The questionnaire asked commentors to first indicate the project location for which
they wanted to provide input and the mode they were using when traveling by the project (walking,
biking, driving, or “other”). Commenters were then asked to compare their experience before and after
the project was installed, rating their comfort level from “very uncomfortable” to “very comfortable.”
Those who did not have “before” experience to draw from were asked to just provide feedback on their
current experience at the project site. An overall summary of feedback received on projects is provided
below; the attached draft evaluation report provides additional detail. Note this summary is for feedback
solicited immediately following the installation of VZIP projects. Feedback solicited on the proposed
recommendations is still being gathered and will be summarized in the presentation delivered at the
December TAB meeting in advance of the public hearing.
Of the 318 Formstack comments presented, a few major themes emerged, including concerns regarding
impacts to parking, the aesthetics of the VZIP projects and skepticism regarding whether they would be
effective. The corridors receiving the highest number of Formstack comments were the Quince corridor
(90 comments), Aurora corridor (36 comments), Glenwood from Folsom to 28th (22 comments),
Glenwood from 29th to 30th (21 comments), the Mohawk corridor (20 comments) and 26th and Spruce
(18 comments).
• Quince Avenue: The primary concerns on the Quince corridor regarded the narrowed travel
lanes (including concerns with large vehicles navigating the installations and navigating in
winter conditions), confusion with how to properly travel through the treatments (and related
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concerns with pedestrians/bicyclists conflicting with vehicles), and concerns with visual
appearance. The most positive feedback themes regarded appreciation for reduced speeds and
safer crossing conditions.
• Aurora Avenue: The primary concerns on the Aurora corridor regarded larger vehicles
navigating the traffic circle, unsafe interactions around curb extensions between vehicles and
cyclists, and concerns with project aesthetics. The most positive feedback shared support for
enhanced crossing safety, particularly for those accessing High Peaks Elementary School.
• Glenwood Drive (Folsom Street to 28th Street): The primary concerns on this segment of
Glenwood included confusion with how to properly navigate the installations, concerns with the
aesthetic appearance, and parking removal. The most positive feedback shared support for
reduced vehicle speeds and better crossing visibility.
• Glenwood Drive (29th Street to 30th Street): The primary concerns on this segment of
Glenwood involved the reduced number of parking spaces and confusion with how to properly
navigate the installations. The most positive feedback shared support for reduced vehicle speeds
and better crossing visibility.
• Mohawk Avenue: The primary concerns on the Mohawk corridor regarded the anticipated
adverse impact to snowplows, concerns with the aesthetic appearance, and unsafe interactions
within the pinch point between vehicles and cyclists. The most positive feedback shared support
for better crossing visibility.
• 26th Street and Spruce Avenue: The primary concern at this intersection involved cyclists
feeling constrained navigating the curb extensions. The most positive feedback shared support
for reduced vehicle speeds, better crossing visibility, and more protection from vehicles.
PROPOSED PROJECT RECOMMENDATIONS
Table 1 summarizes the proposed project recommendations. Of the 25 project locations evaluated, 17
are recommended to be kept, three modified, and five removed.
Table 1. Proposed Project Recommendations
Project Street Device Overall Recommendation
NSMP Related VZIP Projects
Aurora Ave Curb Extensions (Evans Dr.) Remove
Curb Extensions (38th St.) Keep
Curb Extensions and Median
(37th St.)
Keep
Curb Extensions and Traffic
Circle (35th St.)
Keep
Glenwood Dr (east of 28th St) Curb Extension and Pinch Points Remove
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Glenwood Dr (west of 28th St) Curb Extension Modify
Pinch Points Modify
Grinnell Ave Pedestrian Median Island Keep
Mohawk Dr Curb Extensions and Medians
(south of Inca Pkwy)
Remove
Curb Extensions, Medians, Pinch
Point (south of Pitkin Dr)
Remove
Palo Pkwy Median Remove
Curb Extension and Pinch Point Keep
Quince Ave Pinch Points Keep
Curb Extension (17th St) Keep
Chicane Keep
VZIP Pedestrian Crossing Enhancement Projects
10th St and University Ave Median Island Keep
17th St and Grove St Curb Extensions/Art Keep
18th St and Grove St Curb Extensions/Art Keep
19th and Yarmouth Ave Pavement Art Keep
23rd St and Canyon Blvd Curb Extension Keep
9th St and Cascade Ave Curb Extension Keep
Baseline Rd and Mohawk Dr Hardened Centerline Keep
King’s Ridge Blvd High Visibility Crosswalk Keep
Spine Rd and Chaparral Rd Curb Extensions and Median
Island
Modify
Spruce St and 26th St Curb Extensions/Art Keep
STAFF RECOMMENDATION
Staff requests that TAB support the proposed recommendations resulting from the VZIP evaluation
study.
TRANSPORTATION ADVISORY BOARD ACTION REQUESTED
TAB is asked to review the evaluation report, community feedback, and public hearing comment and to
consider a recommendation to endorse finalizing the proposed project recommendations.
Suggested Motion Language:
Motion to recommend finalizing the proposed project recommendations for staff to implement
changes at project sites, as necessary, in early to mid-2023.
NEXT STEPS
Following the outcome of the December TAB meeting, staff will finalize the evaluation report and
project recommendations, with consideration of any suggested TAB revisions. Staff will plan to
implement changes at project sites, as necessary, in early to mid-2023. Staff will consider the lessons
learned from the VZIP evaluation with respect to future decisions about where, when, and why
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innovative, quick-build projects might be most appropriate and effective, including potential ways to
incorporate projects of this type on the Core Arterial Network (CAN), Neighborhood GreenStreets,
streets intersecting CAN corridors, future Safe Routes to School projects, or at existing or planned
pedestrian crossing treatment locations.
For more information regarding the VZIP, please see the VZIP project website.
ATTACHMENTS
Attachment A – Vision Zero Innovation Program 2020-2021 Projects Map
Attachment B – Draft Vision Zero Innovation Program Evaluation Report, December 2022
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Vision Zero
Innovation Program
Legend
NSMP Related VZIP Corridors
VZIP Installation
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Vision Zero Innovation Program Evaluation Report
December 2022DRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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Contents
Executive Summary ...........................................................................................1
Vision Zero Innovation Program Overview....................................................................1
Evaluation Overview .............................................................................................................1
Project Recommendations .................................................................................................2
A. Introduction ...................................................................................................4
Purpose of the Vision Zero Innovation Program (VZIP) ............................................4
Purpose of this Evaluation Report ...................................................................................6
B. Traffic Calming Best Practices and Guidance ..........................................7
Safety Benefits of Traffic Calming ....................................................................................7
Design Speed Reduction Best Practices ......................................................................9
Pros and Cons of Quick Build Horizontal Treatments .............................................12
Design Considerations ......................................................................................................13
Data Driven Analysis ..........................................................................................................15
C. Project Data Summary ................................................................................18
Data Collection and Analysis Methodologies ..........................................................18
D. Lessons Learned and Guidance for Future Treatments ......................23
Lessons Learned ................................................................................................................23
Project Recommendations and Design Guidance ..................................................26
E. Public Feedback Summary ........................................................................33
Feedback Gathering Process .........................................................................................33
Online Feedback Summary .............................................................................................34
F. Evaluation and Decision-Making Framework ........................................36
Framework Overview ........................................................................................................36
G. Conclusion ...................................................................................................38
Overall VZIP Program Reflection ...................................................................................38
H. Appendices ...................................................................................................39
For an electronic version of this document, please visit:
bouldercolorado.gov/projects/vision-zero-innovation-programDRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
12.12.22 TAB Agenda 4 VZIP Evaluation and Next Steps
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Table of Figures
Figure 1. VZIP Project Locations ............................................................................................................1
Figure 2. Traffic Circle and Curb Extensions at Aurora Avenue and 35th Street ...................6
Figure 3. Effects of Traffic Calming Measures ..................................................................................10
Figure 4. Change in Pedestrian counts at VZIP Pedestrian Safety Projects ..........................18
Figure 5. Change in Average Speed at NSMP Related VZIP Projects .......................................19
Figure 6. Change in 85th Percentile Speed at NSMP Related VZIP Projects .........................20
Figure 7. Change in Percent of Vehicles ≥30 MPH at NSMP Related VZIP Projects ...........21
Figure 8. Change in Percent of Vehicles ≥25 MPH at NSMP Related VZIP Projects ...........22
Figure 9. Chicane and Median Island on Quince Avenue .............................................................28
Figure 10. Median Island and Curb Extensions on Mohawk Drive at Inca Parkway ..............29
Figure 11. Chicane on Upland Avenue ..................................................................................................29
Figure 12. Pinch Point on Quince Avenue ............................................................................................30
Figure 14. Speed Kidney on Cherry Avenue ........................................................................................30
Figure 13. Pinch Point on North Ford Street in Golden, CO ...........................................................30
Figure 15. Aerial View of Speed Kidney .................................................................................................30
Figure 16. Traffic Circle on Aurora Avenue ..........................................................................................31
Figure 17. VZIP Projects Map on the VZIP Webpage ........................................................................33
Figure 18. FAQs on the Project Webpage .............................................................................................33
Figure 19. VZIP Project Evaluation Flowchart ....................................................................................36
Figure 20. Public Outreach Poster ..........................................................................................................37DRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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Evaluation Overview
The project team developed an evaluation flowchart (see Figure 19) to understand each project’s
effectiveness at meeting three key goals:
1) Reducing vehicle speeds
2) Improving safety and comfort for street users
3) Ease of maintenance
In 2020, Boulder City Council allocated $250,000 to the Transportation and Mobility (T&M) Department
to support the city’s goal of achieving zero serious injury and fatal traffic deaths, known as Vision
Zero. T&M staff programmed a portion of this funding for the Vision Zero Innovation Program (VZIP),
to speed delivery of projects that would support the city’s Vision Zero goal. During 2020 and 2021,
T&M staff implemented VZIP quick-build projects on six corridors and at six intersections across the
city, with the goal of increasing safety for cyclists and pedestrians (a map of VZIP projects is shown
in Figure 1). VZIP’s cost-effective installations were intended to accelerate progress toward creating
more comfortable and safer streets, supporting neighborhood petitions submitted through the
Neighborhood Speed Management Program (NSMP) and locations identified by community members
as locations of concern.
Vision Zero Innovation Program Overview
Executive Summary
The VZIP was structured to support existing city
programs and intended to inform the applicability
of innovative treatment types for future projects.
The program implemented a variety of treatment
types, including:
• Chicane (1 location)
• Curb extensions (17 locations)
• Pavement art with curb extensions
(3 locations)
• Hardened centerline (1 location)
• Median island (3 locations)
• Pinch point (4 locations)
• Traffic circle (1 location)
Vision Zero
Innovation Program
Legend
NSMP Related VZIP Corridors
VZIP Installation
Figure 1. VZIP Project LocationsDRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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To understand whether projects reduced vehicle speeds, the project team collected before and
after speed-related data near VZIP project locations, and calculated average speeds, 85th percentile
speeds, the percent of vehicles traveling greater than or equal to 25 mph, and the percent of vehicles
traveling greater than or equal to 30 mph. The evaluation framework also considered whether the
average speed after installation was within 3 mph of the speed limit.
To understand whether projects improved safety and comfort for street users, the project team reviewed
community feedback submitted via a Formstack questionnaire posted on the project webpage, and
calls and emails to city staff to evaluate whether each VZIP project increased pedestrian and cyclist
comfort. Signs were also placed on-site, near VZIP installations, to encourage community members to
provide feedback. Over 300 community responses were submitted during the outreach period prior to
and following installation. The evaluation recommendations also considered whether the project was
located on a Neighborhood GreenStreet or bike route.
To understand whether projects are easy to maintain, the project team consulted with the City of
Boulder Fire Department and Transportation Maintenance staff, including staff in charge of street
sweeping and snow removal. The evaluation recommendations considered whether each VZIP project
had any significant impact on the ability of these personnel to conduct emergency and maintenance
operations.
Project Recommendations
Given the ability of each project to meet the three goals outlined above, the project team determined
whether to keep installations in place, modify the project, or remove the project. For project
recommended for removal, staff may consider another project in the long-term, or in conjunction with
work planned through the Core Arterial Network (CAN). These projects will also remain on the NSMP
Complex Project list and may be reconsidered for funding in the long-term. The table below details
evaluation recommendations at each VZIP location.
Project Street Device Overall
Recommendation
NSMP Related VZIP Projects
Aurora Ave.
Curb Extensions (Evans Dr.)Remove
Curb Extensions (38th St.)Keep
Curb Extensions and Median (37th St.)Keep
Curb Extensions and Traffic Circle (35th St.)Keep
Glenwood Dr. (East of 29th
St.)Curb Extensions and Pinch Point Remove
Glenwood Dr. (West of
28th St.)
Curb Extension (Glenwood Ct.) Modify
Pinch Point (between Eastwood Ct and Arnett St) Modify
Grinnell Ave.Pedestrian Median Island (W. of Knox Dr.)Keep
Mohawk Dr.
Curb Extensions and Medians (S. of Inca Pkwy.)Remove
Curb Extensions, Median, and Pinch Point (S. of
Pitkin St.)RemoveDRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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Project Device Overall
Recommendation
NSMP Related VZIP Projects
Palo Pkwy.Median (W. of Palisade Dr.)Remove
Curb Extensions and Pinch Point (Paonia St.)Keep
Quince Ave.Curb Extension and Pinch Points (W. of 17th St.)Keep
Curb Extension and Chicane (W. of 19th St.)Modify
Pedestrian Safety VZIP Projects
10th St. and University
Ave.Median Islands Keep
17th St. and Grove St.
Intersection Curb Extensions and Pavement Art Keep
18th St. and Grove St.
Intersection Curb Extensions and Pavement Art Keep
19th St. and Yarmouth Ave.
Intersection Pavement Art Keep
23rd St. and Canyon Blvd.
Intersection Curb Extension Keep
9th St. and Cascade Ave.
Intersection Curb Extension Keep
Baseline Rd. and Mohawk
Ave. Intersection Hardened Centerline Keep
King’s Ridge Blvd.High Visibility Crosswalk Keep
Spine Rd. and Chaparral
Ct.Curb Extensions and Median Island Modify
Spruce St. and 26th St.
Intersection Curb Extensions and Pavement Art KeepDRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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The VZIP intends to create slower and more comfortable streets for active users through a targeted
application of speed-reducing and pedestrian safety treatments. Grounded in the city’s 2014 adoption
of Vision Zero and in support of the 2019 Transportation Master Plan (TMP), the VZIP takes a data-
driven approach to addressing speeding, which contributed to one out of every three serious crashes
within the city between 2018-2020. The “20 Is Plenty” ordinance adopted in Summer 2020 aligns with
these goals and supports the policy of reducing vehicle speeds in residential areas to mitigate the risk
of high injury crashes.
CREATE SLOWER AND MORE COMFORTABLE STREETS
The City of Boulder’s Vision Zero Innovation Program (VZIP) is intended to deliver quick-build,
innovative, and community-responsive projects to enhance bicycle and pedestrian safety. VZIP is one
of several city programs aimed at achieving Boulder’s Vision Zero goal of eliminating fatalities and
serious injuries caused by traffic crashes. VZIP projects were installed at locations identified either
through safety analyses such as the 2019 Safe Streets Report, sourced from Neighborhood Speed
Management Program (NSMP) community-driven petitions, or via staff’s community engagement
efforts specific to the VZIP in 2021.
VZIP projects that originated from the NSMP were previously evaluated by staff and included on the
NSMP Complex Project list per review and recommendation by the Transportation Advisory Board
(TAB). These projects were not prioritized for funding when VZIP was created, and were identified by
staff as having been impacted by the “20 Is Plenty” ordinance which lowered speed limits on local,
residential streets from 25 mph to 20 mph. Because these streets were evaluated for the NSMP when
they had 25 mph speed zones, “20 Is Plenty” effectively widened the gap between the speed limit
and the observed highest 85th percentile speed used to qualify for the NSMP. Staff felt that these
circumstances created more of a need to address NSMP traffic calming requests, which is why the
locations were prioritized for VZIP projects.
The VZIP program’s goals are to slow speeds to foster more comfortable streets, support ongoing
Vision Zero efforts, test new and innovative traffic calming treatments, and implement measures in a
cost-effective and efficient manner. This report details how each project advances these goals.
Purpose of the Vision Zero Innovation Program (VZIP)
A. Introduction
SUPPORT AND INFORM CONCURRENT MULTIMODAL PROGRAMS
Another objective of the VZIP is to support related city programs, informing the applicability of
innovative treatment types like the speed kidney for future projects. One such program is the NSMP, for
which demonstrated demand exceeds the program’s usual $250,000 annual budget. There is a backlog
of locations on the list of complex projects (differentiated from simple projects in that they are located
on emergency response corridors and require treatment modifications to accommodate and reduce
delay for emergency vehicles). Since the NSMP’s inception in 2017, only one or two complex projects
were planned or implemented annually prior to the program’s pause. Examples of recently completed
NSMP complex corridor projects include 55th St between Baseline Rd. and Omaha Pl. and 26th St. DRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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between Jay Rd. and Kalmia Ave. Bolstered by community support from the NSMP, VZIP treatments
were delivered on a total of five NSMP Complex Project corridors (including Aurora Avenue, Glenwood
Drive, Grinnell Avenue, Mohawk Drive, Palo Parkway and Quince Avenue) as an interim solution to
address speeding concerns and speed limit reductions originating from the “20 Is Plenty” ordinance.,.
Another related effort is the Low‐Stress Walk and Bike Network Plan, which envisions a safe and
low-stress network of multimodal routes complemented by wayfinding and prioritized connections to
key destinations. Within this network-level effort is the development of Neighborhood GreenStreets,
which are low-traffic streets designated by pavement markings, signage, and crossing treatments
to foster comfortable and safer travel environments for all ages and abilities. Most of the streets
that received VZIP treatments are on planned GreenStreets. Additionally, a more recent emphasis
for the overall Vision Zero program is building a more multimodal Core Arterial Network (CAN) to
reduce severe crashes on Boulder’s main arterials through the installation of safety treatments on 13
arterial corridors over the next several years. VZIP projects may inform short-term treatments such as
hardened centerlines or curb extensions on the CAN, or can be used to support connections to CAN
corridors.
TEST INNOVATIVE HORIZONATAL TRAFFIC CALMING TREATMENTS
The VZIP is an opportunity to assess traffic calming treatments that are new to the city of Boulder,
including a speed kidney, which may be the first of its kind in North America. It is also an opportunity
to pilot traffic calming treatments before installing permanent capital projects. The program focused
on horizontal speed deflection treatments including chicanes, curb extensions, hardened centerlines,
median islands, pinch points and traffic circles since temporary vertical treatments may not be
compatible with snow removal during winter storms. Horizontal treatments are intended to slow
vehicles by either visually narrowing the roadway or by causing drivers to change their travel path to
navigate around the devices. Horizontal treatments typically do not result in significant reductions
in traffic volumes and may be less effective than vertical deflection devices like speed humps in
reducing vehicle speeds. The speed kidney, however, is an example of combining both horizontal and
vertical deflection because it gives drivers the option to travel through curvilinear cutouts or over the
component humps.
IMPLEMENT HORIZONTAL TRAFFIC CALMING TREATMENTS QUICKLY AND
AFFORDABLY
A further benefit of the VZIP is its capacity to deliver horizontal traffic calming treatments quickly
and affordably. Typical transportation projects may have lengthy implementation timelines due to the
sequencing of design, approvals, and funding. To help achieve Vision Zero goals, it is important for city
staff to deliver project improvements which are responsive to community needs and expectations. The
low-cost, quick-build nature of these treatments allows for flexibility and modification, given changing
conditions, data collection results, and feedback from internal stakeholders and the community.
Furthermore, the COVID-19 pandemic’s impact on the City of Boulder’s budget prompted a further
desire to work efficiently with reduced funding. Though most treatments consist of paint and plastic
post (delineator) installations, city staff collaborated with local artists where feasible to beautify the
installations and reflect community character.DRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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Purpose of this Evaluation Report
The purpose of this report is to develop a framework to evaluate the effectiveness of treatments
installed in 2020 and 2021, and to recommend where to keep, modify, or remove VZIP treatments
based on consideration of both objective and subjective evaluation criteria. The report should provide
guidance to staff on the general effectiveness of specific treatment types for consideration in future
projects.
EVALUATE EFFECTIVENESS OF VZIP TREATMENTS
Many factors influenced the effectiveness of VZIP treatments installed in more than two dozen
locations across the city, including device spacing, street width, neighborhood traffic volumes, the
frequency of driveways or curb cuts, and more. This report provides an evaluation of these installations
and recommendations for their continued use.
OUTLINE PROCESS FOR FUTURE EVALUATIONS
Additionally, this report provides a barometer for future evaluations by establishing a process to
determine the effectiveness of VZIP-type treatments through the analysis of various measures of
effectiveness. The evaluation results will help guide when, where, and how particular treatments are
chosen and installed within the city.
PROPOSE FRAMEWORK FOR TREATMENT EVALUATION AND
RECOMMENDATIONS
Additionally, this report provides a barometer for future evaluations by establishing a process to
determine the effectiveness of VZIP-type treatments through the analysis of various measures of
effectiveness. The evaluation results will help guide when, where, and how particular treatments are
chosen and installed within the city.
Figure 2. Traffic Circle and Curb Extensions at Aurora Avenue and 35th StreetDRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
12.12.22 TAB Agenda 4 VZIP Evaluation and Next Steps
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Traffic calming is an important component of multimodal transportation networks because it can help
bike and pedestrian traffic feel safer and more comfortable, and can reduce the severity of crashes by
reducing vehicle speeds. Speed reduction has a positive correlation in reducing crash severity, which
is a core tenant of Vision Zero. The Institute of Transportation Engineers (ITE) defines traffic calming
as:
“The combination of mainly physical measures that reduce the negative effects of motor
vehicle use, alter driver behavior, and improve conditions for non-motorized street users.”1
There are both safety and quality of life benefits afforded by traffic calming; in addition to speed
reduction traffic calming devices can also increase sight distances and improving motorist awareness
of pedestrians and cyclists. Targeted traffic calming can support neighborhood-based bikeways
connecting to separated facilities, or efforts to prioritize non-vehicular street users through “Shared
Street” installations or closures. Traffic calmed neighborhood streets also support community
expectations for these places: that they are safe for children and pets, and free from reckless drivers.
CRASH MODIFICATION FACTORS (CMFS)
According to the FHWA, Crash Modification Factors (CMFs) “…is a multiplicative factor used to
compute the expected number of crashes after implementing a given countermeasure at a specific
site.”2 These estimates can be helpful for calculating cost/benefit ratios and when deciding between
appropriate treatment types. Countermeasures with CMFs under 1 demonstrate a crash reducing
effect (i.e., a countermeasure with a CMF of 0.70 would estimate a 30-percent crash reduction).
The CMFs for various treatment types are detailed below.
• For the countermeasure “median treatment for ped/bike safety” (Crash Modification Factors
Clearinghouse):
○Three of the four CMFs listed in the Clearinghouse demonstrated a decrease in crashes
○Crash Reduction Factor (CRF) of 86-percent for fatal pedestrians and cyclist related crashes
(0.14 CMF)
○CRF of 14 (0.86 CMF) for all crashes, not exclusive to pedestrians and cyclists
1 Lockwood, I. (1997). ITE Traffic Calming Definition. In ITE Journal (p. 22). Retrieved from https://www.ite.org/technical-
resources/traffic-calming/
2 U.S. Department of Transportation. (n.d.). (issue brief). Local and Rural Road Safety Briefing Sheet: Crash Modification
Factors (CMFs). Retrieved from https://highways.dot.gov/sites/fhwa.dot.gov/files/2022-06/cmf.pdf
B. Traffic Calming Best Practices and
Guidance
Safety Benefits of Traffic Calming
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• For the countermeasure “convert two-way stop-controlled intersection to roundabout” for 1-2
lane roads in the Suburban area type (NCHRP Applying Roundabouts in the United States):
○All six of the CMFs listed in the Clearinghouse demonstrated a decrease in crashes
○The CMFs ranged from 0.22-0.81
The 2022 Vision Zero Boulder: Safe Streets Report identified crash types of concern, including those
involving making a left turn (34-percent of severe crashes), speeding (32-percent of severe crashes),
impairment (11-percent of severe crashes) and distraction (7-percent of severe crashes). Targeting
engineering modifications at locations of concern based on identified crash types most effectively
addresses safety needs. For example, the VZIP installed a hardened centerline on the east leg of the
intersection at Baseline Road and Mohawk Drive, which was one of two locations in the city with the
highest number of severe left-turn crashes between 2018 and 2020. The device was installed to reduce
vehicular turning radii, reduce speeds, and increase the visibility of interactions between vehicles and
active users in the crosswalk.
Aside from the Baseline Rd. and Mohawk Dr. location, the VZIP project locations do not address
crash trends. It is important to note that this evaluation did not include conducting a crash analysis
given the lack of documented crash trends in project areas. However, during the design process, the
project team considered mitigating measures to reduce any potential crash risk and severity, such as
considering sight lines, material durability, and vehicle turning paths. The inclusion of CMF information
in this section of the report is meant as guidance for consideration in future projects, especially those
that are located on higher-volume arterials like Baseline Rd.
RELATIONSHIP BETWEEN SPEED AND CRASH SEVERITY
Lowering vehicle speeds is highly effective in decreasing the severity of crashes involving active users,
should they occur. According to ITE3, the chance of a fatal vehicular-pedestrian crash increases from
10-percent at a vehicle speed of 20 mph to 80-percent at 40 mph. The 2022 Safe Streets Report found
that speeding is a contributing factor in one out of every three severe crashes within the city. While
these crashes occurred almost exclusively on arterials, it’s important to consider the relationship
between speed and crash severity when addressing speeding concerns throughout the city, including
on local and collector streets.
INCREASE VISIBILITY OF ACTIVE USERS AND IMPROVE SIGHT DISTANCES
Traffic calming treatments can enhance pedestrian and cyclist safety by increasing sight distances at
corners (also called daylighting) and enhancing visibility of crossing locations, both at intersections
and mid-block. The Burlington Public Works Quick Build Design + Materials Standards4 guide
recommends using a street’s desired target speed (rather than the posted speed) to design ideal sight
distance triangles and maximize visibility. Treatments such as curb extensions, median islands, and
3 Institute of Transportation Engineers. (n.d.). Speed as a Safety Problem. ITE: A Community of Transportation
Professionals. Retrieved from https://www.ite.org/technical-resources/topics/speed-management-for-safety/speed-as-a-
safety-problem/
4 Street Plans, DuBois & King, & Local Motion. (n.d.). (rep.). Burlington Public Works Quick Build Design + Materials
Standards. Retrieved from https://www.burlingtonvt.gov/sites/default/files/QUICK_BUILD%20GUIDE_0.pdfDRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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street murals can assist with delineating sight triangles for vehicles while reducing crossing distances
and, in the case of street art, providing beautification. Cities across the country have had success
putting these daylighted areas to beneficial use for active modes, such as Hoboken, NJ’s targeted
approach which have contributed to the city’s lack of traffic fatalities (0 since 2018).5
Design Speed Reduction Best Practices
This chapter will review best practices for achieving targeted design speed reductions, including
treatment design guidance for device spacing to maximize traffic calming effectiveness. Traffic
calming project design is dependent on local conditions, including street width, driveway/curb cut
spacing, drainage considerations, and concerns from property owners or residents. In Boulder, traffic
calming projects have historically been designed starting with guidance from ITE and the sources
below, but adjusted for local considerations. Design guidance, including device width, height, and
spacing, should continue to be determined with context sensitivity in mind.
SPACING OF DEVICES TO ACHIEVE DESIRED VEHICLE SPEEDS
• Spacing observations for plastic delineators
○The Tactical Urbanist’s Guide recommends placing flex posts every 8-10 feet within curb
extensions.6
• Spacing observations for pinch points
○The National Association of City Transportation Officials (NACTO)’s guidance recommends
that pinch points reduce the two-way travel path to less than 18 feet, with 12 feet
recommended.7
• Spacing observations for median islands
○Pennsylvania’s Traffic Calming Handbook advises that medians be 6-8 feet wide and 12-20 feet
in length to maximize user comfort.8
• Spacing observations for traffic circles
○The NACTO Urban Street Design Guide recommends traffic circles provide approximately 15
feet of clearance from the widest point of the circle to the nearby corners.9
○Pennsylvania’s Traffic Calming Handbook advises that a series of traffic circles are most
effective at reducing speeds.10
5 Nielsen, A. (2022, June 21). New Jersey City ‘Weaponizes’ Parking Rules to Cut Traffic Fatalities. The Crime Report.
Retrieved from https://thecrimereport.org/2022/06/20/new-jersey-city-weaponizes-parking-rules-to-cut-traffic-fatalities/
6 Street Plans Collaborative. (2016). (rep.). Tactical Urbanist’s Guide to Materials and Design. Retrieved from http://
tacticalurbanismguide.com/
7 NACTO. (2014). (rep.). Urban Bikeway Design Guide: Speed Management. Retrieved from https://nacto.org/publication/
urban-bikeway-design-guide/bicycle-boulevards/speed-management/
8 Pennsylvania Department of Transportation. (2012). (rep.). Pennsylvania’s Traffic Calming Handbook. Retrieved from
https://www.dot.state.pa.us/public/pubsforms/Publications/PUB%20383.pdf
9 NACTO. (2014). (rep.). Urban Bikeway Design Guide: Speed Management. Retrieved from https://nacto.org/publication/
urban-bikeway-design-guide/bicycle-boulevards/speed-management/
10 Pennsylvania Department of Transportation. (2012). (rep.). Pennsylvania’s Traffic Calming Handbook. Retrieved from
https://www.dot.state.pa.us/public/pubsforms/Publications/PUB%20383.pdfDRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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ABILITY OF VARIOUS HORIZONTAL AND VERTICAL TREATMENTS TO REDUCE
SPEED AND VOLUMES
The figure below provides a description of the types and effectiveness of different traffic calming
treatments based primarily on guidance from peer cities, such as Pennsylvania’s Traffic Calming
Handbook, from which Figure 2 is sourced (yellow arrows are placed to the left of treatments installed
through the VZIP). Note that the data outlined below typically refers to concrete applications of
treatments versus quick build, and therefore VZIP results may vary slightly.
Figure 3. Effects of Traffic Calming Measures
VZIP TREATMENT TYPES
Chicane
Treatment Details: Chicanes are created by an off-set paring or series of curb extensions, which require
drivers to slow down to navigate an S-shaped travel path. The chicane installed through the VZIP is
designed for one-way traffic; it is too narrow for two vehicles to proceed side-by-side and therefore
requires street users to yield to one another.
Impact: According to Pennsylvania’s Traffic Calming Handbook11, chicanes have the potential to reduce
vehicle speeds within the treatment itself by 5-13 mph and by 1-6 mph for vehicles approaching or
departing the device. The Federal Highway Administration (FHWA)’s Engineering Speed Management
Countermeasures Table estimates a speed reduction of 6-9 mph based on case studies in two-lane
11 Pennsylvania Department of Transportation . (2012). (rep.). Pennsylvania’s Traffic Calming Handbook. Retrieved
from https://www.dot.state.pa.us/public/pubsforms/Publications/PUB%20383.pdfDRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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rural communities and a reduction in the 85th percentile speed of 16-percent on an urban road and
29-percent on other roads. The Pennsylvania Handbook estimated traffic volume reductions upwards
of 20-percent on streets with chicanes as well.
Curb Extensions
Treatment Details: Curb extensions, which are also called neck downs or bulb-outs, are typically
installed at intersections and can provide an extension of the sidewalk further into the roadway,
reducing the crossing distance for active users and narrowing the roadway. Vehicles making right
turns are slowed as well. Mid-block installations may be beneficial at locations of high pedestrian
traffic, such as near schools or multiuse paths.
Impact: According to Pennsylvania’s Traffic Calming Handbook, curb extensions reduce speeds by
1-2 mph on average; however, speeds may be reduced up to 5 mph if lane widths are significantly
narrowed (to between 18-20 feet total, which is most applicable on low volume streets).
Hardened Centerline
Treatment Details: Hardened centerlines create a raised center feature which narrows lane widths,
promoting slower speeds and safer left-turns. Hardened centerlines make it more difficult for drivers
to make longer, wider maneuvers that sweep across a larger crosswalk section when turning, which
can reduce exposure for pedestrian and cyclists in crosswalks. Instead, left-turning vehicles follow a
reduced turning radii that creates a more perpendicular intersection with the crosswalk.
Impact: According to the City of Kingston, Ontario’s Traffic Calming Guidelines12, centerline treatments
have the potential to reduce speeds by up to 5 km/h (roughly 3 mph).
Median Island
Treatment Details: Median islands provide a center refuge area for pedestrians and cyclists to wait for
a gap in vehicle traffic before completing their crossing.
Impact: According to Pennsylvania’s Traffic Calming Handbook, the most prevalent speed reductions
that were observed following the installation of median islands were 2-3 mph, though the range was up
to 5 mph. Speed reductions are greater when lanes are narrowed in conjunction with median islands,
or when there is more horizontal deflection in the vehicle travel path.
Pinch Point
Treatment Details: Pinch points (also called chokers) are mid-block curb extensions that narrow the
travel way. Pinch points can narrow a street to a one lane roadway, which creates yielding conditions,
or can maintain two-way traffic with two lanes. In the case of two-way pinch points, drivers may feel
less comfortable passing oncoming traffic, resulting in slower speeds. Both types of pinch points were
installed though the VZIP. Pinch points may also be called curb extensions in some contexts.
Impact: The FHWA estimates a 1-4 mph speed reduction following pinch point installation. 13
12 U.S. Department of Transportation. (2014, July). Engineering Speed Management Countermeasures: A Desktop
Reference of Potential Effectiveness in Reducing Spee. Retrieved from https://safety.fhwa.dot.gov/speedmgt/ref_mats/
13 City of Kingston. (n.d.). (rep.). Traffic Calming Guidelines. Retrieved from https://www.cityofkingston.ca/
documents/10180/15058/Traffic+Calming+Guidelines.pdf/804c309a-7195-ba08-e20e-dd17349f0a53?t=1629998980890DRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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Speed Kidney
Treatment Details: A speed kidney features a grouping of three speed humps, with an oval-shaped
hump straddling the center of the road and one “kidney” shaped hump on each side within the travel
lanes aligning with the center oval’s curvature.
Impact: According to the City of Kingston, Ontario’s Traffic Calming Guidelines, speed kidneys may
result in up to a 5 km/h (roughly 3 mph) reduction in speeds. The potential for traffic volume reductions
depends on the number of speed kidneys installed along the roadway.
Traffic Circle
Treatment Details: Neighborhood traffic circles are installed at unsignalized intersections and typically
consist of raised or delineated islands which traffic must negotiate in a circular manner. Yield signs
may be placed to govern safe travel patterns.
Impact: According to Pennsylvania’s Traffic Calming Handbook14, traffic circles have the potential to
reduce speeds by 4-6 mph. The reduction in traffic volumes is typically minor, though jurisdictions
have reported 10- to 20-percent reductions.
Pros and Cons of Quick Build Horizontal Treatments
The major benefits and critiques of the VZIP’s quick-build treatments are detailed below and offer
lessons learned for future modifications to traffic calming treatments of this nature.
LIFE CYCLE OF QUICK BUILD VERSUS PERMANENT TREATMENTS
When determining the cost benefit ratio of quick build treatments versus permanent installations, it
is crucial to consider the life cycle implications of materials like paint and plastic posts (delineators)
which are intended to be interim in nature versus more hardened materials like concrete.
PROS
There are several pros to quick build treatments, namely:
• Opportunity for in-house design and installation (with targeted help from vendors). The
design phase of a typical project may involve a series of iterations, ensuring design standards
and budgetary realities are met. Hiring outside consultants may be beneficial to support city
staff, but can increase costs and may lengthen the timeframe between design and installation.
The VZIP relied primarily on city staff to complete the design and installation of treatments.
• An accelerated installation timeline. VZIP treatments were implemented during the spring/
summer months (with multiple treatments installed in a single day), a task which would have
been infeasible for a typical series of concrete projects.
14 Pennsylvania Department of Transportation . (2012). (rep.). Pennsylvania’s Traffic Calming Handbook. Retrieved from
https://www.dot.state.pa.us/public/pubsforms/Publications/PUB%20383.pdfDRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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• Greatly reduced cost. The paint and post style delivery of VZIP treatments resulted in significant
cost reductions compared to concrete capital projects (in general, quick-build treatments
each cost in the thousands vs. the $10,000 to hundred thousand dollar cost of concrete capital
projects; a savings of approximately 10 times).
• Ability to modify designs flexibly and creatively. VZIP treatments were iterative in their design
and installation. Staff was able to monitor conditions at the treatment sites and efficiently adjust
elements of the design, when warranted.
• Ease of project removal should a maintenance/operational concern or data finding warrant
it. A further benefit of the quick-build nature of VZIP treatments is the ability to remove or adjust
elements as needed. The removal costs and timeframe for typical concrete projects would far
exceed the flexibility of paint and post modifications or removals.
CONS
There are also several cons to consider with quick build treatments, namely:
• Reduced lifecycle. Quick-build, paint and post treatments are less durable than their concrete
counterparts, with a reduced ability to withstand serious impacts and increased chance of
damage to device materials. Figures from the Denver Department of Transportation and
Infrastructure (DOTI)’s Vertical Elements Study15 estimated that typical concrete elements have a
50-year life cycle, with “floating” elements having closer to a 25-year life cycle. Vertical elements
would be replaced every 10 years during a street’s mill/overlay cycle (assuming damage prior-to
did not warranted replacement). Elements like flex posts are designed to be unscrewed, but DOTI
encountered issues removing them safely all in one piece.
• Appearance. Following VZIP treatment installation, there was some concern among Boulder
community members that the treatments appeared ugly, unfinished, or akin to a construction
zone. Though a handful of treatments were paired with artistic additions, this was not possible
for all treatment types or locations due to budgetary restrictions, installation timelines, and
maintenance concerns.
• Maintenance concerns. As noted above, though the lifecycle of paint and post treatment types
varies, additional maintenance may be required when compared to concrete installations. This
factor led city staff to anticipate snowplow blade movements and emergency vehicle response
clearance during design, acknowledging that in real-world conditions durability may vary.
Design Considerations
To maximize the effectiveness of traffic calming treatments, it is crucial to determine the roadway
context and review the impact to essential maintenance, snow removal and emergency response
service providers.
15 Denver Department of Transportation and Infrastructure. Vertical Elements Study. November 2021.DRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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CONTEXT CONSIDERATIONS
When considering which are the most appropriate traffic calming treatment types for a given street,
roadway width should be considered given its influence on vehicle speeds. Street width is a starting
point to determine whether various treatments will fit within the given curb-to-curb space.
Adjacent land use, whether it be residential, commercial, industrial, or a combination of these,
influences the effectiveness of different treatment types. Design vehicles should be appropriate for
the level of access needed (e.g., on emergency routes or in very dense neighborhoods). Consideration
of traffic calming devices needs to include whether they may impede vehicle types. For example, on
corridors with high truck traffic or frequent buses, chicanes may not be appropriate, given geometric
needs for navigating the treatment.
The presence and density of on street parking can impact a project installation as well, and guides
discussions regarding parking removal or clear space surrounding an installation. Some devices may
be more appropriate with on-street parking given available street space, and depending on the street
context. For example, where off-street parking is limited, it may make more sense to select traffic
calming devices that do not significantly reduce on-street parking availability.
Furthermore, the presence of pedestrian facilities like sidewalks and crosswalks can influence design
considerations. For example, in areas where no sidewalks are present (as in a rural North Boulder
context like on Quince Avenue), designs must consider where pedestrians will navigate the traffic
calming treatment on the street, which necessitates identifying pinch points where user types
may overlap. Curb extensions and median islands are recommended for installation where existing
crosswalks are present.
IMPACT TO MAINTENANCE AND SNOW REMOVAL OPERATIONS
When first determining the applicability of various quick build improvements, it is crucial that
maintenance and snow removal teams are included in the design process, as treatment decisions
should be made so as not to impede regular maintenance activities (like street sweeping) and
accommodate snow removal equipment on city streets slated for plowing. Potential treatment types
may be eliminated based on concerns regarding snow removal operations, such as armadillos (small,
elliptical shaped bumps used to create physical delineation), which can prove challenging for plows to
see and avoid during heavy snow accumulation.
In Boulder, initial community concerns arose prior to the first snow season following the installation of
VZIP treatments. City staff worked with the City Attorney’s Office to clarify snow clearing obligations
for curb extensions adjacent to sidewalks, including property owner responsibility to clear a five-foot
path on curb ramps and extensions within 24 hours after snow stops falling. The 2021 - 2022 snow
season demonstrated that minor adjustments would benefit plowing operations proximate to VZIP
projects, such as along Palo Parkway at Paonia Street (where curb extensions and a pinch point are
installed), and where staff’s recommendation was to maintain the installation but also consider snow
removal on the north side of the street (in Boulder County’s jurisdiction).DRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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IMPACT TO EMERGENCY RESPONSE
Prioritizing emergency access (including fire, police, and other emergency response personnel)
remains a critical factor when determining the design of traffic calming treatments. It is important
to discuss turning radii and lane width requirements with fire and police departments to ensure
compatibility. For example, according to Pennsylvania’s Traffic Calming Handbook16, traffic circles
may incur a delay anywhere from 1-11 seconds per circle, with most delays in the 5-8 second range. A
good starting point for discussions includes expectations for safe navigation and a determination of
whether to avoid installations on critical emergency response corridors.
There is precedent for close coordination in the development of traffic calming projects in Boulder
through the NSMP Complex Projects design process, wherein treatments (such as speed cushions)
are designed for these critical corridors with accommodations for emergency vehicles like fire trucks.
A similar coordination process with first responders was used prior to the installation of the VZIP
treatments.
Data Driven Analysis
Below is a summary of data-driven evaluations typical for quick-build treatments with an overview of
findings specific to the VZIP’s treatments.
INTERIM TREATMENT EVALUATION PROCESS
The evaluation process for the city’s VZIP treatments included gathering before and after data based
on the treatment type and project purpose or intent (e.g., traffic calming, slower turning speeds,
crossing comfort, etc.). Data collection may gather average speeds, 50th and 85thpercentile speeds,
the number of speeding vehicles (going either greater than 5 mph or greater than 10 mph over the
speed limit), average daily traffic volumes, peak hour turning movement counts, and additional,
modal-specific data such as pedestrian crossing counts. The goal of such evaluations is to determine
whether the installed treatments achieved the desired conditions (i.e., a reduction in average speed
or reduction in the number of high-end speeding vehicles – i.e., over 30 mph on neighborhood streets).
BEST PRACTICES FOR DATA COLLECTION
Effective before and after data collection studies attempt to ensure similar conditions for both
collection timeframes. Key factors which were considered in data collection for this evaluation study
include:
• Weather (i.e., not collecting before data in summer months and after data in snowy months)
• Time of day (i.e., not collecting before data at rush hour and after data at noon)
• Day of week (i.e., not collecting before data on Monday and after data on Sunday)
• Seasonal conditions at location (i.e., not collecting before and after data in front of a school
during the summer and after data while school is in session)
• Temporary changes at location (i.e., not collecting data when construction is occurring one
block down the street)• Allowance for conditions to normalize (i.e., it is best not to collect after data until at least 6
months post construction)
16 Pennsylvania Department of Transportation . (2012). (rep.). Pennsylvania’s Traffic Calming Handbook. Retrieved from
https://www.dot.state.pa.us/public/pubsforms/Publications/PUB%20383.pdfDRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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DATA SUMMARIES
Chicanes
A chicane was installed on Quince Avenue west of 19th Street (and paired with pinch points and
curb extensions).
Before and after speed studies near the chicane demonstrated a 10-percent reduction in the
average speed (from 22 mph to 20 mph) and 8-percent reduction in the 85th percentile speed (from
26 mph to 24 mph). There were noteworthy reductions in vehicles traveling at 30 mph or higher (a
71-percent reduction) and in vehicles traveling at 25 mph or higher (a 64-percent reduction).
Curb Extensions
Curb extensions were installed in 11 locations and featured an arrangement of 36-inch-tall plastic
delineators (referred to previously in this report as “posts”) with bolted bases (placed 7-15 feet
apart). Curb extensions were the most widely installed traffic calming element placed on corridors
which also received other treatments, including marked crosswalks/crossing treatments, median
islands, traffic circles, and pinch points. At 26th Street and Spruce Street, Grove Street and 17th
Street, and Grove Street and 18th Street, artistic treatments were painted within the delineator-
protected space.
Before and after speed studies near curb extensions demonstrated an average reduction in speeds
of 3-percent. The average 85th percentile speed reduction proximate to curb extension locations
was 4-percent. The average reduction in vehicles traveling at 30 mph or higher and at 25 mph or
higher were similar at just under 30-percent reduction.
The most effective VZIP curb extension location was on Aurora Avenue at 35th Street, which was
paired with a traffic circle. This location saw a 14-percent reduction in average speed, 16-percent
reduction in the 85th percentile speed, 94-percent reduction in vehicles traveling at 30 mph or
higher and 77-percent reduction in vehicles traveling at 25 mph or higher.
Hardened Centerline
A hardened centerline consisting of a rubber speed bump and a traffic separator curb with vertical
panels was installed on the east leg of the intersection of Baseline Rd at Mohawk Drive. Delineator
posts were installed on the centerline on Mohawk Drive between Aurora Avenue and Inca Parkway.
The before and after studies conducted near the hardened centerline treatment evaluated
vehicle turning paths to observe whether vehicles crossed after or at/ahead of the median. For
those vehicles making a southbound left turn movement from Mohawk Drive onto Baseline Road
(eastbound), 23-percent crossed after the median before project installation and 91-percent did
after. These conditions improve vehicle and pedestrian interactions by ensuring vehicles are more
squarely facing pedestrians in the crosswalk as they complete their turn, and not driving over a
larger section of the crosswalk prior to the turn.
Additionally, 15-percent of vehicles making a U-turn on Baseline Road (westbound) crossed after
the median before project installation and 36-percent did after. Though not as significant of an
improvement for this vehicle movement, there is still a measurable safety benefit to the corrected
vehicle path. DRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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Median Island
Standalone median islands were installed at two locations as a solo treatment type. At another two
locations, median islands were paired with additional treatments, including curb extensions and
pinch points.
Before and after studies on Palo Parkway near Palisade Drive, which was one of the locations with a
standalone median island, demonstrated no effectiveness in reducing speeds, with a slight increase
in overall recorded speeds.
However, before and after speed studies at Grinnell Avenue west of Knox Dive, the other standalone
median island location, showed an 18-percent reduction in the 85th percentile speed, a 97-percent
reduction in vehicles traveling at 30 mph or higher and 94-percent reduction in vehicles traveling at
25 mph or higher. Generally, the width of the median treatment and the street appear to play a larger
role in horizontal deflection on Grinnell Avenue than at other locations.
Studies conducted at locations where a median island was paired with other treatments like on Aurora
Avenue near 37th Street and Mohawk Drive near Inca Parkway demonstrated around 5-percent speed
reduction. On Mohawk Drive the number of top speeders (those traveling at or above 30 mph) was
reduced by 30-percent.
Pinch Points
Pinch points were installed at five locations and paired with other corridor treatments including curb
extensions and median islands.
Before and after speed studies where pinch points were installed demonstrated a 5-percent or less
reduction in average and the 85th percentile speed. There was not a noticeable difference between
these figures when pinch points were installed alone versus paired with other treatments. Studies
conducted at locations where a pinch point was installed did reduce the number of top speeders
(those traveling at or above 30 mph) by an average of 25-percent, with the greatest reduction (of
70-percent) seen on Quince Avenue.
Speed Kidney
A speed kidney was installed on Cherry Avenue near 9th Street, potentially the first installation of the
treatment in North America.
Before and after speed studies at this location demonstrated a 12-percent reduction in average speed
and 17-percent reduction in 85th percentile speed. The reduction in higher end speeders was more
significant, with a 98-percent reduction in vehicles traveling at 30 mph or higher and 90-percent
reduction in vehicles traveling at 25 mph or higher.
Traffic Circle
A traffic circle was installed on Aurora Avenue at 35th Street.
Before and after speed studies at this location demonstrated a 14-percent reduction in average speed
and 16-percent reduction in 85th percentile speed. The reduction in higher end speeders was more
significant, with a 94-percent reduction in vehicles traveling at 30 mph or higher and 77-percent
reduction in vehicles traveling at 25 mph or higher.DRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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C. Project Data Summary
Data Collection and Analysis Methodologies
To quantitatively evaluate the effectiveness of VZIP traffic calming treatments and determine the
effectiveness and applicability of various treatment types long-term, staff collected detailed before
and after data at VZIP project locations.
DATA SUMMARY
The summary tables below provide high-level data-driven analysis of VZIP treatments. More detailed
tables can be found in the Appendix.
Pedestrian Counts
Before: Counts conducted between 2016 -2019 / After: 2022 counts
Figure 4. Change in Pedestrian counts at VZIP Pedestrian Safety ProjectsDRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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Average Vehicle Speed
Before: Counts conducted between 2018 -2021 / After: 2022 counts
Figure 5. Change in Average Speed at NSMP Related VZIP ProjectsDRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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85th Percentile Vehicle Speed
Before: Counts conducted between 2018 -2021 / After: 2022 counts
Figure 6. Change in 85th Percentile Speed at NSMP Related VZIP ProjectsDRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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High-End Speeding Vehicles
Before: Counts conducted between 2018 -2021 / After: 2022 counts
Figure 7. Change in Percent of Vehicles ≥30 MPH at NSMP Related VZIP ProjectsDRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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High-End Speeding Vehicles
Before: Counts conducted between 2018 -2021 / After: 2022 counts
Figure 8. Change in Percent of Vehicles ≥25 MPH at NSMP Related VZIP ProjectsDRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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D. Lessons Learned and Guidance
for Future Treatments
Lessons Learned
The VZIP was intended to bring innovative, quick-build improvements to Boulder streets to enhance
pedestrian and cyclist safety and comfort. The nimble nature of project installations allowed for
adjustments as needed post installation. Usual challenges were factored into the VZIP Project
Evaluation Flowchart (Figure 17) and provided lessons learned for the future applicability of installing
these treatments elsewhere in the city.
POST-INSTALLATION CHANGES TO TREATMENTS
Chicane (Quince Avenue)
After monitoring community feedback and considering appropriate changes, staff determined that a
few minor modifications were needed.
Prompting concerns to address:
• Motorists feeling constrained to the right of the approach island
• Motorists parking in the area to the right of the approach island
• A lack of clarity that cyclists have option to take the lane or stay to the right of the island
• Pedestrians feeling “pinched” when walking between approach islands
Staff changes included:
• Adjusted the location of the “No Parking Any Time” signs to more clearly convey that the space to
the right of the approach islands is not for vehicle parking
• Installed green-backed bike lane symbol markings in the area to the right of the approach islands
• Removed yellow delineators and mini “Keep Right” signs on the painted median island
WHAT’S WORKED WELL
Partnerships with Local Artists
At three VZIP curb extension installations (26th Street and Spruce Street, Grove Street and 17th Street
and Grove Street and 18th Street) artistic treatments were painted within the bollard-protected space.
Community members expressed support for the neighborhood beautification and local artists were
given an opportunity to promote their skills. While these works of art are popular with community
members, longevity and maintenance should be considered before installation.DRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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Reducing High End Speeds at a Low Cost
After installation data at two VZIP project locations demonstrated a 90-percent or more reduction in
high end speeders (those traveling at 30 mph or more), including the traffic circle with curb extensions
on Aurora Avenue at 35th Street and speed kidney at Cherry Avenue near 9th Street. At two additional
project locations (the chicane paired with pinch points and curb extensions on Quince Avenue west
of 19th Street and the pinch point on Quince Avenue west of 15th Street) a still-significant 70-percent
reduction in high end speeders was achieved.
CHALLENGES
Emergency, Transit and Maintenance Vehicle Design
Emergency, transit, and maintenance vehicles (such as street sweepers and snowplows) require
tailored design considerations in comparison to a typical personal vehicle. Though project staff made
every attempt to design treatments to accommodate these priority vehicles, issues did arise in the
field, such as with the traffic circle on Aurora Avenue which required tweaks to ensure emergency
and transit vehicle access was not hindered. The Fire Department also expressed concerns about the
median posts in the chicane on Quince Avenue, which prompted modifications for that VZIP treatment
while still in the evaluation period. Staff ultimately decided to remove the yellow median delineators in
the chicane given ongoing emergency response and street sweeping concerns.
Effectiveness vs. Public Perception
In order for traffic calming measures to be effective, they modify typical, unrestrained driving patterns
through physical and visual modifications to the travel way. These challenges inherently require
additional attention to navigation (such as the yielding conditions at a chicane or a reduction in turning
radius at curb extensions). Modifying the typical, unrestrained movements may feel bothersome and
challenging to community members. Such changes often garnered negative public feedback.
Parking Occupancy Considerations
The project team attempted to minimize impacts to parking, however the removal of parking was
required to allow room for some VZIP installations. In some cases, curbside space near intersections
that was previously used for parking was replaced with curb extensions which were intended to
improve sight distances and visibility. Though not formally signed as so, these spaces are technically
illegal to park within, due to their proximity to the intersection (the Boulder Revised Code [7-6-13]
prohibits parking within 30-feet of a stop sign, 20-feet of an intersection or crosswalk, and 5-feet of a
fire hydrant).
Though concerns regarding parking constraints or removal of spots to accommodate VZIP treatments
arose for nearly every corridor, a few in particular (Glenwood Drive, Aurora Avenue, Quince Avenue
and Mohawk Drive) spurred the most comments. Approximately 20 spots were removed on Glenwood
Drive between Folsom Street and 30th Street (0.5 miles) and 12 spots on Aurora Avenue between 35th
Street and Mohawk Drive (0.4 miles).DRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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Of the 318 recorded comments, about 15-percent (46) mentioned parking. A few comments were
positive in nature (support for reducing illegal parking at intersections and near school drop-off/
pick-up zones) but the majority shared concerns, including “bottlenecking” style conditions created
through parking removal, issues accessing parking lots, the challenge of needing to park further away
and walk when walking short distances is challenging, reduced parking near residences, and impacts
to visitor and service vehicle access, particularly at apartment complexes along Glenwood Drive.
Pedestrian and Cyclist Considerations
Pedestrians and cyclists shared concerns and confusion with the project team regarding how best to
safely navigate various treatment types. Some active users shared concerns with feeling “pinched” by
interactions where travel lane widths were reduced, particularly where sidewalks were not present (as
on Quince Avenue).
Staff launched a messaging campaign to communicate navigation expectations for different users
through various treatment types, including adding a Frequently Asked Questions (FAQ) document
to the project webpage clarifying that cyclists should either travel with traffic or through the posts,
depending on their comfort level, and pedestrians should stay on the inside of the installations and
travel through them to cross the street.
Snow Removal
Following initial community concerns, T&M staff partnered with the City Attorney’s Office to clarify
snow clearing obligations for curb extensions adjacent to sidewalks. T&M and legal staff found that
property owners are responsible for clearing a five-foot path on curb ramps and extensions within 24
hours after snow stops falling. This finding aligns with Boulder Revised Code requirements for property
owners clearing sidewalks of snow during winter storms, treating the VZIP curb extensions like
permanent sidewalk extensions. For the most part, this approach was well-received and demonstrated
high snow clearing compliance rates.
Maintenance Costs
When budgeting for VZIP treatments, staff attempted to quantify projected costs for on-going
maintenance, including delineator replacement, restriping, and artistic touch-ups. Overall, sign
shop and maintenance staff did not communicate significant impacts to workgroup programs, but
did indicate that VZIP installations at Aurora Avenue and 35th Street, Mohawk Drive south of Inca
Parkway, and Spine Road near Chaparral Court are difficult to maintain. This feedback was included
in the development of recommendations for each of the treatments documented in the decision-
making process flowchart.DRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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VZIP VERSUS NSMP
The VZIP was designed as a testing ground for quick-build, horizontal traffic calming treatments –
building off the success of more permanent vertical treatments (typically speed humps and speed
cushions) installed through the NSMP. In general, before and after data collected on NSMP corridors
where vertical speed treatments were installed demonstrated a 15‐20-percent reduction in 85th
percentile speeds. In comparison, the average 85th percentile speed reduction for VZIP (typically
horizontal) treatments was 5%.
For comparison of the VZIP vs. the NSMP, two streets that have similar existing conditions such as
roadway width and adjacent land use (residential with few driveways) are Aurora Avenue (VZIP) and
55th Street south of Baseline Road (NSMP). Each street had similar traffic volumes prior to project
installation, around 2,000 average daily traffic (ADT) and similar 85th percentile speeds (Aurora Avenue
had a top recorded 85th percentile speed of 29 mph, 55th Street had a top 85th percentile speed of
35 mph). One key difference in the two streets is that Aurora Avenue has space for on-street parking,
but because 55th Street is much narrower functionally lane widths are similar. While Aurora Ave.
received a traffic circle and series of curb extensions through the VZIP, demonstrating between a 14
and 5-percent change in 85th percentile speeds, 55th Street received a series of five speed cushions
that reduced speeds up to 20-percent. Vertical deflection devices tend to lead to greater reductions
in vehicle speeds, though device design and spacing matters in both vertical and horizontal device
applications.
Project Recommendations and Design Guidance
The following section includes a level summary of installations that should be removed, modified,
or kept. These recommendations are based on before and after installation data analysis, review of
public feedback, and consultation with the Boulder Fire Department and Transportation Maintenance
Division. This section also includes design considerations for future projects, as well as general design
guidance to apply to project development.
PROJECT RECOMMENDATIONS
Based on the evaluation findings from this report, staff’s recommendation for each VZIP device is
summarized in the table below.
Project Street Device Overall
Recommendation
NSMP Related VZIP Projects
Aurora Ave.
Curb Extensions (Evans Dr.)Remove
Curb Extensions (38th St.)Keep
Curb Extensions and Median (37th St.)Keep
Curb Extensions and Traffic Circle (35th St.)Keep
Glenwood Dr. (East of 29th
St.)Curb Extensions and Pinch Point Remove
Glenwood Dr. (West of
28th St.)
Curb Extension (Glenwood Ct.) Modify
Pinch Point (between Eastwood Ct and Arnett St)ModifyDRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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Project Device Overall
Recommendation
NSMP Related VZIP Projects
Grinnell Ave.Pedestrian Median Island (W. of Knox Dr.)Keep
Mohawk Dr.
Curb Extensions and Medians (S. of Inca Pkwy.)Remove
Curb Extensions, Median, and Pinch Point (S. of
Pitkin St.)Remove
Palo Pkwy.Median (W. of Palisade Dr.)Remove
Curb Extensions and Pinch Point (Paonia St.)Keep
Quince Ave.Curb Extension and Pinch Points (W. of 17th St.)Keep
Curb Extension and Chicane (W. of 19th St.)Modify
Pedestrian Safety VZIP Projects
10th St. and University
Ave.Median Islands Keep
17th St. and Grove St.
Intersection Curb Extensions and Pavement Art Keep
18th St. and Grove St.
Intersection Curb Extensions and Pavement Art Keep
19th St. and Yarmouth Ave.
Intersection Pavement Art Keep
23rd St. and Canyon Blvd.
Intersection Curb Extension Keep
9th St. and Cascade Ave.
Intersection Curb Extension Keep
Baseline Rd. and Mohawk
Ave. Intersection Hardened Centerline Keep
King’s Ridge Blvd.High Visibility Crosswalk Keep
Spine Rd. and Chaparral
Ct.Curb Extensions and Median Island ModifyDRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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TREATMENTS TO MODIFY
Quince Chicane: Median Island
During the VZIP evaluation period, staff
moved the “No Parking” signs and put in bike
symbols to address community concerns.
After completing the VZIP Project Evaluation
Flowchart for Quince Avenue projects, staff
has decided to remove the yellow median
delineators in between the white islands in
the chicane west of 19th Street (see Figure 9).
Though the chicane achieved speed reduction
targets and met comfort-related goals, the city’s
maintenance team shared street sweeping
concerns and the fire department found
navigation unnecessarily difficult. Overall, the
chicane met the speed reduction goals of the
VZIP.
Spine and Chaparral Median Island and Curb Extensions
Like the median island on Quince Avenue, the one at this intersection achieved comfort-related
goals but posed maintenance concerns including for street sweeping and snowplow clearance. The
placement of the delineators on both the median island and curb extensions should be further set
back allowing for more vertical clearance in the travel lane. Overall, the enhanced pedestrian crossing
met the safety and comfort goals of the VZIP.
Glenwood Avenue Curb Extensions and Pinch Point West of 28th Street
VZIP installations on Glenwood Avenue west of 28th Street, curb extensions at the Two-Mile Creek
Path crossing and Eastwood Court, and a pinch point near Arnett Street, have met speed reduction
and pedestrian safety goals for the program. However, feedback from community members has
indicated that cyclists feel uncomfortable sharing space with vehicles, so staff recommends modifying
the spacing of delineators and adding “bike dots” to make it clearer that cyclists have the option to
navigate between the delineators. Sign shop and maintenance staff also expressed that the posts
need more regular maintenance than other installations, which may be alleviated by slightly setting
back the delineators from the pavement markings.
TREATMENTS TO REMOVE
Palo Median Island
The median island on Palo Parkway west of Palisade Drive did not cause significant deflection or travel
lane narrowing and was also ineffective at meeting speed reduction goals. The device did not meet
the speed reduction goals of the VZIP and is recommended for removal.
Figure 9. Chicane and Median Island on Quince Avenue
DRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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Figure 11. Chicane on Upland Avenue
Aurora Curb Extensions at Evans Drive
The curb extensions on Aurora Avenue at Evans Drive did not achieve speed reduction goals as a
standalone treatment. Staff plans to maintain the installation only until the upcoming Safe Routes
to School (SRTS) project (expected to begin construction in Spring/Summer 2023) replaces the paint
and posts with concrete curb extensions. The goal of the SRTS is to enhance the pedestrian crossing
rather than reduce speeds; paired with a relocated flashing school zone sign and hardscape, concrete
curb extensions, and marked and signed crosswalk, staff expects the SRTS project to improve driver
awareness of children and parents traveling by foot or bike to High Peaks Elementary School.
Mohawk Drive Treatments
After completing the VZIP Project Evaluation Flowchart for
Mohawk Drive projects, staff decided to remove all treatments
installed on Mohawk Drive, including the curb extensions and
medians south of Inca Parkway (pictured in Figure 10) and the curb
extensions, median and pinch point south of Pitkin Street. These
treatments were overall ineffective at meeting speed reduction
goals. Further feedback indicated that cyclists felt less comfortable
biking on the street post-project installation, which factored in the
recommendation to remove these devices.
Figure 10. Median Island and Curb
Extensions on Mohawk Drive at Inca
Parkway
Curb Extension and Pinch Points on Glenwood Avenue East of 28th Street
The VZIP installations on Glenwood Avenue east of 28th Street did not result in significant speed
reduction (around 2-percent). Paired with parking concerns voiced by community members, and the
realization that modifying the devices to have greater impacts on speeds would encourage drivers
to veer left of the centerline, staff recommends that the VZIP devices used on this street are not
adequate to meet project goals.
TREATMENTS TO KEEP
Chicane
Before and after studies conducted at the chicane
on Quince Avenue demonstrated a noticeable
reduction in high-end speeding vehicles including
those traveling at 30 mph or higher (a 71-percent
reduction) and those traveling at 25 mph or higher (a
64-percent reduction). In addition to the VZIP chicane,
city staff installed another quick-build chicane on
nearby Upland Avenue, using parking wheel stops and
crusher fines. Both projects offer support for exploring
chicane installations elsewhere in the city.DRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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Pinch Points
Figure 12. Pinch Point on Quince Avenue Figure 13. Pinch Point on North Ford Street in Golden, CO
Before and after studies conducted at VZIP locations where a pinch point was installed reduced the
number of top speeders (those traveling at or above 30 mph) by an average of 25-percent. Quick
build pinch points hold promise as cost-effective speed reduction measures, with potential for more
permanent concrete installations, including landscaping (such as in Figure 13).
Speed Kidney
The VZIP speed kidney was an innovative design, potentially the first installation of the treatment in
North America. Before and after speed studies at this location demonstrated only moderate reductions
in average speed and 85th percentile speed, but significant reductions in higher end speeders, with
a 98-percent reduction in vehicles traveling at 30 mph or higher and 90-percent reduction in vehicles
traveling at 25 mph or higher. The speed kidney offered a valuable messaging opportunity with the
Boulder community, paving the way for future applications in the city.
Figure 14. Speed Kidney on Cherry Avenue Figure 15. Aerial View of Speed KidneyDRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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Traffic Circle
Figure 16. Traffic Circle on Aurora Avenue
Before and after studies
conducted at the traffic
circle on Aurora Avenue at
35th Street demonstrated
significant reductions in
higher end speeders, at a
94-percent reduction in
vehicles traveling at 30 mph
or higher and 77-percent
reduction in vehicles traveling at 25 mph or higher. Staff made initial tweaks to the curb extensions
to accommodate larger vehicles, and though there may be potential to modify materials over time to
reduce maintenance needs, the traffic circle’s design holds promise for providing significant speed
reductions on neighborhood streets.
PARKING OCCUPANCY AND PERCEIVED IMPACTS
On Aurora Avenue, staff received a considerable number of concerns that VZIP project installation was
reducing parking on the corridor. This concern was primarily related to peak parking needs on Aurora
Avenue during pick-up/drop-off for the Boulder Community School of Integrated Studies (BCSIS).
Staff met with residents to discuss their concerns and clarify locations where parking restrictions
were simply formalized through VZIP project installation (as at curb extension locations on corners
near stop signs).
Staff also received initial concerns from Glenwood Drive residents living in apartment complexes
along the corridor near where the pinch point was installed between 29th Street and 30th Street.
(Staff met with residents to discuss concerns and acknowledged some loss of parking that could be
impactful during peak parking hours. This feedback was factored into the recommendation to remove
the VZIP installations on Glenwood Avenue east of 28th Street.
DESIGN SPEED
The VZIP projects derived from the NSMP were developed with a design speed of 20 mph, to match
speed limits. In determining the appropriate device width and horizontal clearance of each device, as
well as spacing from one device to another, several factors needed to be considered. These included
on-street parking zones, and the locations of fire hydrants, crosswalks, curb ramps, and driveways/
curb cuts. Drainage was also a consideration, as VZIP-style treatments may create areas where street
sweeping cannot reach debris that may accumulate next to a curb. These considerations, as well
as coordination with emergency and maintenance staff, often would take precedence over design
speed decisions leading to greater speed reduction. Another important consideration project design
is community feedback and acceptance, which needs to be balanced with targeted outcomes set by
using a design speed. Some flexibility is important when considering design speeds and contextual
factors.DRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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DESIGN VEHICLE CONSIDERATIONS
Staff determined several crucial metrics to keep in mind during VZIP treatment design to ensure
treatments remained effective in achieving speed reduction goals while also accommodating the
variety of vehicles navigating Boulder’s streets.
Control Vehicle Types
Generally, traffic calming designs should accommodate turning movements for an SU-30 design
vehicle (for some local streets a DL-23 vehicle may be appropriate). An SU-30 vehicle is a 30-feet long,
single unit vehicle typical of most local delivery vehicles.
Emergency Response Vehicle Design Guidelines
In addition to design vehicle turning movements, adequate horizontal and vertical clearance will
need to be maintained for emergency response vehicles. Generally, 12-foott horizontal clearance (lane
width) from pavement edge to traffic calming device is preferrable for emergency vehicles. Vertical
deflection should accommodate emergency vehicles (either through cut-outs like those used in
speed cushions, or by designing an adequate width speed table that will allow for both wheel axles to
top the table before the front axle departs the device. The fire department should be consulted in the
design of traffic calming projects prior to installation.
Maintenance Vehicle Design Guidelines
Like emergency response vehicles, maintenance vehicles should have adequate horizontal and vertical
clearance to perform essential functions like street sweeping and snow removal. For VZIP-style (paint
and post) installations, delineators should be set back from pavement markings 12 – 18 inches to allow
for sweepers and plows to clear the markings, while also providing at least a 13-foot wide opening
between the base of posts [a plow blade is 11-feet wide. Permanent traffic calming devices should not
depart from widely accepted design practices and in the case of vertical devices, be traversable by
maintenance vehicles. Street operations should be consulted in the design in traffic calming projects
prior to installation. DRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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Vision Zero
Innovation Program
Legend
NSMP Related VZIP Corridors
VZIP Installation
Figure 17. VZIP Projects Map on the VZIP Webpage Figure 18. FAQs on the Project Webpage
E. Public Feedback Summary
Feedback Gathering Process
Project staff recognized that upfront and consistent messaging with the community regarding VZIP
projects would be critical, given their quick-build nature and the application of new-to-Boulder
treatments (such as the speed kidney). Staff worked closely with the City of Boulder Communications
and Engagement Department to create an informative webpage, including videos, descriptions of
treatment types, and FAQs, modifying the page to address concerns as they arose.
ONLINE FEEDBACK
Though staff received VZIP project related phone calls, emails, and tickets through Inquire Boulder (the
city’s customer service portal), the majority of VZIP feedback (over 300 comments) were submitted
through a Formstack questionnaire on the project webpage. The questionnaire asked commentors
to first indicate the project location for which they wanted to provide input and the mode they were
using when traveling by the project (walking, biking, driving, or “other”). Commenters were then asked
to compare their experience before and after the project was installed, rating their comfort level from
“very uncomfortable” to “very comfortable.” Those who did not have “before” experience to draw from
were asked to just provide feedback on their current experience at the project site.DRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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CHALLENGES
Though the project team worked closely with the Communications and Engagement Department to
provide upfront information and address concerns as they arose, VZIP projects did lead to community
member and resident concerns, particularly regarding parking impacts, the aesthetic appearance of
the treatments, and yielding to oncoming traffic conditions that the installations created.
The COVID-19 pandemic posed further challenges to communications, considering many project staff
were working from home and health regulations encouraged limited in-person interaction between
residents and staff.
Online Feedback Summary
Of the 318 Formstack comments presented, a few major themes emerged, including concerns
regarding impacts to parking, the aesthetics of the VZIP projects and skepticism regarding whether
they would be effective.
OVERALL FEEDBACK SUMMARY
The corridors receiving the highest number of Formstack comments were the Quince corridor (90
comments), Aurora corridor (36 comments), Glenwood from Folsom to 28th (22 comments), Glenwood
from 29th to 30th (21 comments), the Mohawk corridor (20 comments) and 26th and Spruce (18
comments).
Quince Avenue: The primary concerns on the Quince corridor regarded the narrowed travel
lanes (including concerns with large vehicles navigating the installations and navigating in winter
conditions), confusion with how to properly travel through the treatments (and related concerns with
pedestrians/bicyclists conflicting with vehicles), and concerns with visual appearance. The most
positive feedback themes regarded appreciation for reduced speeds and safer crossing conditions.
Aurora Avenue: The primary concerns on the Aurora corridor regarded larger vehicles navigating the
traffic circle, unsafe interactions around curb extensions between vehicles and cyclists, and concerns
with project aesthetics. The most positive feedback shared support for enhanced crossing safety,
particularly for those accessing High Peaks Elementary School.
Glenwood Drive (Folsom Street to 28th Street): The primary concerns on this segment of Glenwood
included confusion with how to properly navigate the installations, concerns with the aesthetic
appearance, and parking removal. The most positive feedback shared support for reduced vehicle
speeds and better crossing visibility.
Glenwood Drive (29th Street to 30th Street): The primary concerns on this segment of Glenwood
involved the reduced number of parking spaces and confusion with how to properly navigate the
installations. The most positive feedback shared support for reduced vehicle speeds and better
crossing visibility.DRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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Mohawk Avenue: The primary concerns on the Mohawk corridor regarded the anticipated adverse
impact to snowplows, concerns with the aesthetic appearance, and unsafe interactions within the
pinch point between vehicles and cyclists. The most positive feedback shared support for better
crossing visibility.
26th Street and Spruce Avenue: The primary concern at this intersection involved cyclists feeling
constrained navigating the curb extensions. The most positive feedback shared support for reduced
vehicle speeds, better crossing visibility, and more protection from vehicles.
FEEDBACK PRE AND POST REPORT TO COMMUNITY
Prior to the December 12, 2022, Transportation Advisory Board (TAB) public hearing and presentation of
the VZIP Report and project recommendations, staff worked with the Communications and Engagement
Department to update the VZIP project webpage to reflect next steps and encourage community
member feedback. This update included sharing before and after data and the recommendations
for each project location, noting whether staff intended to remove, modify, or keep each installation.
The original Formstack questionnaire was modified to ask residents whether they agreed with staff’s
recommendations. Community members were encouraged to attend the December TAB meeting to
provide their feedback during public comment. DRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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F. Evaluation and Decision-Making
Framework
Framework Overview
The flowchart evaluation framework detailed below outlines a customizable process which will be
modified as needed for new VZIP-type installations moving forward (including if implemented through
NSMP or another process/program). The flowchart is a tool to assist decision-making, but is flexible
enough for staff to discuss the outcomes of each stage of the chart. It is not intended to be overly
prescriptive or not allow for exceptions.
Figure 19. VZIP Project Evaluation FlowchartDRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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PLAN FOR PUBLIC NOTIFICATION
In addition to the December TAB meeting and public hearing, the
project team plans to work with the City Communications and
Engagement Department to share next steps for VZIP project, including
outreach through city social media channels, city newsletters and
Nextdoor. Staff will also install yard signs along VZIP project corridors
that clarify whether treatments will be kept, modified or removed,
and sharing associated data findings.
MODIFICATION PROCESS
For those treatments where the evaluation process determined that
modifying the treatment was the best course of action, staff plans to
work with maintenance staff to understand the best project upgrades
to reduce wear and tear and provide greater durability over time.
Quince Ave.
Vision Zero
Innovation Program
WHAT WE LEARNED
AVERAGE SPEED
Before = 22 mph |
85TH PERCENTILE SPEED
Before = 26 mph |
RECOMMENDATION:
Sta will present this recommendation to the Transportation Advisory
Board (TAB) at their meeting on December 12, 2022. TAB will hold a public
hearing before advising a course of action on this recommendation.
To learn more and share your perspective, visit:
bit.ly/boulder_vzip
PERCENT OF VEHICLES 30 MPH
Before = 2% |
PERCENT OF VEHICLES 25 MPH
Before = 20% |
Aer = 20 mph
Aer = 24 mph
Aer = 1%
Aer = 8%
MODIFY
West of 19th St.
Figure 20. Public Outreach PosterDRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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G. Conclusion
Overall VZIP Program Reflection
Overall, the VZIP demonstrated that Transportation and Mobility staff can deliver low-cost traffic
calming and pedestrian safety projects effectively and more quickly than a traditional transportation
capital project. These projects can be effective in meeting the goals of reducing vehicle speeds and
improving pedestrian and cyclist visibility and crossing comfort. However, to meet these goals there
are tradeoffs, which include impacts to traffic operations and the localized loss of parking spaces in
some scenarios. Furthermore, the Boulder community has expectations for the quality of materials
used in transportation projects, so concerns about the aesthetic appearance of VZIP-style projects
cannot be understated. Communicating the benefits of these types of projects may mitigate some of
the trade-offs and concerns, though city staff should be prepared to discuss the long-term implications
of maintaining installations with policymakers and the community.
VZIP SUCCESS
Generally, VZIP projects met expected speed reduction goals and performed similarly to concrete
capital projects. Some installations were more successful than others due to decisions made during
the design process accounting for the context of each local street and emergency response and
maintenance needs. Staff was able to deliver over 15 projects within a constrained budget in under
one calendar year, which would have been a challenging task if these projects were programmed
through the NSMP or Low-Stress Walk and Bike Network budget as permanent installations.
APPLICABILITY TO OTHER PROGRAMS
Takeaways from the VZIP apply to other city programs and initiatives, including the Core Arterial
Network (CAN), Pavement Management Program Mobility Enhancements and installation of
Pedestrian Crossing Treatments.DRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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H. Appendices
DRAFTAttachment B - Draft Vision Zero Innovation Program Evaluation Report, December 2022
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