HomeMy WebLinkAbout02.14.22 TAB Agenda 6 20 is Plenty EvaluationCITY OF BOULDER
TRANSPORTATION ADVISORY BOARD
AGENDA ITEM
MEETING DATE: February 14, 2022
AGENDA TITLE:
20 is Plenty Evaluation: Staff Briefing and TAB Feedback
PRESENTER(S):
Erika Vandenbrande, Director of Transportation and Mobility
Natalie Stiffler, Deputy Director of Transportation and Mobility
Devin Joslin, Principal Traffic Engineer
Mark Shisler, Principal Project Manager
Mike Gardner-Sweeney, Transportation Operations Engineer for Signals & Lighting
Veronica Son, Transportation Operations Engineer
EXECUTIVE SUMMARY
This memo summarizes the recently completed evaluation of the city’s “20 is Plenty” initiative. The
change to lower the prima facie, or default, speed limit on unposted streets to 20 mph was made through
City Council passage of Ordinance 8395, which amended the Boulder Revised Code section 7-4-58 and
became effective on June 18, 2020. Concurrent with the ordinance passage, staff changed a total of
approximately 465 speed limit signs from 25 mph to 20 mph signs on local streets, where applicable,
and updated the “Welcome to Boulder” gateway signs at the city limits to indicate the citywide 20 mph
default speed limit.
The “20 is Plenty” evaluation included: review of background information related to the ordinance
change; interviews with peer cities who had implemented similar initiatives; analysis of before/after
vehicle speed data; and recommendations related to city projects and programs based on the data
findings and analysis.
The evaluation finds that “20 is Plenty” has not reduced vehicle speeds in a statistically significant way
across key performance indicators: mean speed, 50th, 85th, and 95th percentile speeds, and percent of
vehicles traveling above 30 and 35 mph.
The evaluation found some correlation between roadway characteristics (street width, lane width,
parking density, etc.) and measured vehicle speeds. Streets where measured speeds were higher
commonly included a striped centerline and wider travel lanes. Roadway characteristics such as having a
posted speed limit sign, dense tree canopy or high on-street parking density did not correlate with a
decrease or increase in speeds.
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“20 IS PLENTY” EVALUATION PURPOSE AND GOALS
The purpose of the “20 is Plenty” evaluation was to study whether lowering the speed limit and
changing posted speeds from 25 mph to 20 mph on local streets resulted in reduced vehicle speeds. The
evaluation also provides recommendations to introduce or modify speed management programs,
procedures, and policies to align with the new 20 mph speed limit.
The evaluation had three main goals:
1. To study other cities who have implemented “20 is Plenty” to understand results achieved and
impacts to projects and programs.
2. To evaluate the City of Boulder’s implementation of “20 is Plenty,” focusing on whether it has
resulted in reduced vehicle speeds.
3. To understand how “20 is Plenty” has affected existing projects and programs in the city and
formulate recommendations for changes or enhancements.
PEER CITY INTERVIEW KEY FINDINGS
Interviews with staff from four peer cities were conducted to provide additional insights into
recommendations for speed limit reductions in Boulder. The cities interviewed included: Portland,
Oregon; Eugene, Oregon; Cambridge, Massachusetts; and Seattle, Washington.
Key takeaways from the peer city interviews are organized by topics that were discussed.
Community Engagement
All cities, excluding Seattle, performed some form of marketing and advertising campaigns surrounding
local street speed limit reduction. Press conferences, radio and print campaigns, and social media posts
were most common. Interviewed city staff agreed that the most consistent and successful method for
communicating speed limit changes was the large-scale distribution of yard signs. Peer cities also raised
awareness by collaborating with neighborhood groups, interested residents, and local organizations and
programs including Safe Routes to School.
School Zones and Posted Signage
Cities were asked whether school zone speed limits were reduced to 15 mph, advisory speeds were
adjusted or removed from warning signs, and whether additional speed limit signs had been posted.
None of the peer cities interviewed have lowered school zone speed limits to 15 mph after implementing
speed limit reductions to 20 mph on local streets. This is primarily because of the state government’s
level of control over speed limit setting in Oregon, Washington, and Massachusetts. The City of Seattle
removed advisory speed signs in most cases where the advisory speed corresponded to the newly posted
20 and 25 mph speed limit signs. Multiple municipalities noted that speed limit reductions revealed the
need for a higher frequency of posted speed limit signage, especially on local streets adjacent to arterial
and collector streets, and the need to improve consistency in the placement of speed limit signs.
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Evaluation Process
The City of Portland and the City of Seattle are the only interviewed cities that completed before and
after data analysis of vehicle speeds. Of note, both cities’ studies had constraints like Boulder’s
evaluation in that there was relatively limited before/after data on which conclusions could be drawn. In
addition, it does not appear that these cities accounted for the error (typically ± 1 mph) of their traffic
counters when presenting results.
Portland evaluated speeds before and after the reduction of the local street speed limit from 25 mph to
20 mph in 58 locations and found:
• No change in median speed or 85th percentile speed
• Very small reductions in the percent of drivers traveling greater than 25 (-0.5%), 30 (-1.7%), and
35 (-0.5%) mph
Seattle evaluated speeds before and after spot reductions of the speed limit on arterials in North Seattle
from 30 mph to 25 mph and found:
• Reductions in crashes (-22% for total crashes, -18% for injury crashes)
• Reductions in 50th percentile (-9.9%), 85th percentile speeds (-7.1%), and the percent of drivers
traveling 40 mph or greater (-54.1%)
Updated Methods and Design Programs for Setting and Reinforcing Lower Speed Limits
While design standards and methods for setting speed limits were not significantly affected, cities found
that implementing lower speed limits revealed a need to retrofit streets with traffic calming to reinforce
the lower speed limits. Peer cities noted that the speed limit reductions led to a procedural shift where
staff now design streets for target speeds rather than the 85th percentile speed, which studies have
shown can lead to increases in travel speeds over time. The speed limit reductions also led staff to revise
speed management programs to be more context sensitive and increased the number of streets eligible
for traffic calming projects.
Enforcement
The four cities use a combination of automated enforcement (fixed cameras and photo radar vans), speed
feedback trailers, and fixed speed radar signs to reiterate or enforce the speed limit. Many cities
expressed that enforcement is typically a short-term solution when areas pop up as speeding hotspots
either through resident complaints, staff speed studies and/or staff crash analysis. Cities favored an
engineering approach that redesigns streets to bring speeds down permanently through traffic calming
infrastructure changes rather than using enforcement on an ongoing basis.
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DATA ANALYSIS SUMMARY
Attachment A includes the Draft Evaluation of “20 is Plenty” Summary Report. The draft report
conveys findings in a detailed, yet graphical way, including tables, charts, and maps to highlight results.
Subsequent sections of this memo summarize the findings in simple text form.
The evaluation of “20 is Plenty” used the following vehicle speed data:
• 22 locations with before and after data collected using tube counters
• 10 locations with only after data collected using tube counters
• 6 directional locations with before and after data collected with photo radar vans
In each case, the streets were two-way streets, so data was evaluated separately by each direction of
travel. The data analysis was organized into four parts: comparing key performance indicators,
hypothesis testing, linear regression (after data only), and photo radar van data analysis.
Comparing Key Performance Indicators
Combining all locations with before and after vehicle speed data, the following was concluded:
• Average speed increased 1.62%
• 50th percentile speed, 85th percentile speed, and 95th percentile speed remained unchanged
• Percent of vehicles traveling above 30 mph increased by 1.48%
• Percent of vehicles traveling above 35 mph increased by 0.28%
Hypothesis Testing
Statistical hypothesis testing was conducted for each of the 22 before and after speed locations to see if
the average speeds decreased (with 95% statistical confidence) after the speed limit was lowered from
25 mph to 20 mph. Though on average there were minimal changes in vehicle speeds from before to
after “20 is Plenty,” the results varied by location, as indicated in the below:
• After “20 is Plenty,” the average speed decreased in 17 directions and increased in 27 directions.
Linear Regression (After Data Only)
A linear regression analysis was performed on the locations with after only data to determine to what
extent various roadway characteristics could be attributed to reduced vehicle speeds. The after data only
was used for this analysis since it was a larger set of data, and the intent was to relate how motorists
were driving after the change to 20 mph to roadway characteristics. The regression analysis determined
whether any linear relationship existed between average speeds and roadway characteristics, such as
street width, lane width, presence of striped centerline, presence of speed limit sign, parking density, etc.
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The results of the linear regression analysis suggest:
• Narrower streets/lanes and the absence of a striped centerline correlate with lower average
speeds.
Photo Radar Van Data Analysis
The city currently uses photo radar vans to enforce speed limits on local streets. The van is moved
around to different locations with identified speeding issues. The six directional locations of the photo
radar van with before/after data included 911 hours of before data and 699 hours of after data. The
evaluation showed the following results:
• On average, vehicle speeds changed from 25.6 mph to 23.5 mph (a reduction of 2.1 mph).
• The number of violations per hour increased from 2.5 per hour to 8.4 per hour.
RECOMMENDATIONS
The evaluation identified a total of 23 recommendations to consider across 10 topics corresponding to
various city programs, policies, procedures, and projects.
Neighborhood Speed Management Program
1. Update NSMP engineering toolkit to include the removal of striped centerline markings and
treatments that provide a mix of horizontal and vertical deflection; review guidelines and
industry best practices for speed hump placement along streets with 20 mph speed limits.
2. Launch data-driven speed management program focused solely on arterial streets, involving
community engagement instead of accepting resident applications.
3. Prioritize segments of local streets that adjoin arterial streets.
Designing for Target Speeds
4. Revise the Design and Construction Standards to use a 20 mph target speed for local street
design.
5. Conduct a systematic evaluation of existing local street widths (and speed-related crashes) to
identify segments of concern; prioritize segments of concern for inclusion in future traffic
calming projects or programs such as the NSMP.
Functional Street Classification
6. Identify street segments currently classified as local streets that function as higher classification
roads.
7. Consider reclassifying select streets/street segments from local to collector where the access
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density, transit stop density, emergency response route, snowplow route, and other
characteristics relate more closely to other streets with higher classifications.
8. Consider developing an Industrial Street and Business Park Street classification to better match
streets providing access to industrial and business land uses.
9. Evaluate speed limit reductions along high-crash, high-speed arterial corridors using the speed
limit setting framework that will be developed in the upcoming Community Mobility Planning
and Implementation (CMPI) Speed Limit Setting and Signing Framework grant project.
Additional Speed Limit Reductions to Support Vision Zero
10. Prioritize arterial speed limit reductions on high-stress arterial corridors that also adjoin local
streets where 20 mph speed limits have been introduced.
Speed Limit Setting in School Zones
11. Consider reducing speed limits in select school zones from 20 mph to 15 mph based the school
circulation patterns, sight distance, roadway width, nearby land uses and other various criteria.
12. Working with partners at the Boulder Valley School District, identify potential locations where
School Streets (shared streets in front of schools) could be implemented to best support speed
reductions and encourage mode shift.
Standardizing Sign Practices
13. Through the CMPI Speed Limit Setting and Signing Framework grant, develop a consistent
practice for 20 mph speed limit signing on local streets and at additional key gateway locations
throughout the city.
Warning Signs/Advisory Speeds
14. No changes recommended.
Photo Radar Van Program and Radar Speed Signs
15. Periodically re-evaluate the location of street segments on which to deploy the photo radar vans.
16. Consider lobbying members of the Colorado General Assembly to allow automated enforcement
on arterial streets.
17. Expand the use of both permanent and portable radar speed feedback signs along arterial streets.
Pedestrian Crossing Treatment Installation Guidelines
18. No changes recommended.
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Promotion and Engagement
19. Increase the presence of “20 is Plenty” yard signs and update messaging to incorporate statistics
on speeding crashes, speed enforcement, and community disapproval of speeding.
20. Reintroduce other “20 is Plenty” advertising including media and online efforts to spread
awareness of Vision Zero.
21. Develop a Culture Change Model approach that changes social perceptions of the risks of
speeding.
22. Communicate and collaborate with local organizations and existing programs like Safe Routes to
School to create and promote campaigns specifically targeting drivers who speed.
23. Extend speeding education to reach beyond NSMP project sites.
NEXT STEPS:
Staff welcomes TAB feedback on the findings and recommendations from the “20 is Plenty” evaluation.
Given current City Council priorities, staff has been asked to prioritize and focus resources on arterial
streets. As a result, work on the Neighborhood Speed Management Program and Neighborhood
GreenSreets has been paused. Staff is planning to discuss the “20 is Plenty” findings with City Council
at the March 8, 2022 Study Session and will relay any TAB feedback.
Despite the results of the evaluation, local streets continue to generally not exhibit speed-related crash
patterns, as indicated in the Draft Safe Streets Report, 4th Edition 2022. Thus, the recommendations
presented will need to be balanced against priorities and implemented over time as part of a
comprehensive Vision Zero strategy.
QUESTIONS FOR TAB:
1. What feedback does TAB have regarding the “20 is Plenty” evaluation?
ATTACHMENTS:
Attachment A – Draft Evaluation of “20 is Plenty” Summary Report
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DRAFT | FEBRUARY 2022
20 IS PLENTY
Summary Report
Evaluation of
Attachment A
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This report is provided for informational purposes only, and all results, recommendations, and commentary contained herein are based
on limited data available at the time of preparation. Further planning and policy analysis may be necessary prior to implementing the
recommendations contained herein. Toole Design makes no representations or warranties regarding the accuracy of the underlying source data.
Attachment A
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Contents
What is “20 is Plenty?” ................................................2
Purpose, Goals, and Key Performance Indicators ....2
Purpose ..........................................................................................................2
Goals ...............................................................................................................2
Key Performance Indicators .......................................................................2
Evaluation Method and Results ..................................3
Comparing Key Performance Indicators ..................................................3
Hypothesis Testing .......................................................................................4
Linear Regression – After Data Only ........................................................4
Photo Radar Van Data Analysis..................................................................5
Before and After 85th Percentile Speeds by Location ............................6
Relevant Guidance and Peer City Efforts .................11
Literature Review ......................................................................................11
Reducing Speeds to 20 mph ...........................................................................11
Successful Speed Management Programs ..................................................12
Peer City Interview Key Findings ............................................................12
Communication .................................................................................................12
School Zones and Posted Signage ................................................................13
Evaluation Process ...........................................................................................13
Updated Methods and Design Programs for Setting and
Reinforcing Lower Speed Limits ....................................................................13
Enforcement ......................................................................................................13
Recommendations .....................................................14
Next Steps ..................................................................19
Attachment A
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Evaluation of 20 IS PLENTY Summary Report
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What is “20 is Plenty?”
Across the United States and other countries, there is
an emphasis on lowering speed limits in an effort to
reduce the potential for serious injuries when crashes
occur and to improve the livability of local streets. This
initiative is commonly referred to as “20 is Plenty.” In June
2020, the City of Boulder committed to “20 is Plenty.” City
Council passed an ordinance to lower the prima facie
(also known as default or unposted) speed limit from 25
mph to 20 mph. Concurrent with the ordinance passage,
staff changed a total of approximately 465 speed limit
signs from 25 mph to 20 mph signs on local streets,
where applicable, and updated the “Welcome to Boulder”
gateway signs at the city limits to indicate the citywide 20
mph default speed limit.
The city views “20 is Plenty” as one aspect of its
commitment to achieving Vision Zero, which is the city’s
goal to reduce the number of traffic-related fatalities and
serious injuries to zero. As such, the new 20 mph speed
limit signs include an orange outline and the words “Vision
Zero” across the top of the sign to remind motorists of the
connection of slower speeds to reduced severe crashes.
Evidence suggests there is a greater chance for pedestrian
and bicyclist survival when vehicles are traveling 20 mph
compared to vehicles traveling at higher speeds. Slower
travel speeds on locally-classified residential streets also
increase the likelihood of people driving yielding to people
walking and bicycling and contribute to a more comfortable
environment for people to walk and bicycle.
Purpose, Goals, and Key
Performance Indicators
Purpose
The purpose of this evaluation is to study whether
lowering the speed limit and changing posted speeds
from 25 mph to 20 mph on local streets resulted in
reduced vehicle speeds. The evaluation also provides
recommendations to introduce or modify speed
management programs, procedures, and policies to align
with the new 20 mph speed limit.
Goals
The evaluation had three main goals:
1.To study other cities who have implemented “20
is Plenty” to understand results achieved and
impacts to projects and programs.
2.To evaluate the City of Boulder’s implementation
of “20 is Plenty,” focusing on whether it has
resulted in reduced vehicle speeds.
3.To understand how “20 is Plenty” has affected
existing projects and programs in the city and
formulate recommendations for changes or
enhancements.
Key Performance Indicators
To measure the success of reducing the prima facie speed
limit from 25 mph to 20mph on local streets, before and
after vehicle speed data from 22 locations across the city
was analyzed. This evaluation focused on the following
key performance indicators:
•Percent and number of drivers traveling at
or below 20 mph
•Percent change in mean (average) speed
•Percent change in median (50th percentile) speed
•Percent change and number of drivers traveling
10 mph over the (new) speed limit
•Percent change and number of drivers traveling
15 mph over the (new) speed limit
•Percent change in 85th percentile speed
•Percent change in 95th percentile speed
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Evaluation Method and Results
The evaluation of “20 is Plenty” used vehicle speed data
collected at 22 locations before and after the speed limit
reduction, 10 additional locations with data collected
only after the speed limit reduction, and 6 locations with
photo speed van radar data collected before and after the
speed limit reduction. In each case, the streets were two-
way streets, so data was separated into two directions
of travel. The analysis was organized into three parts:
comparing key performance indicators, hypothesis testing,
and linear regression.
Comparing Key Performance Indicators
Combining all 22 locations with before and after speed
count data to create one citywide dataset created a
dataset of 140,454 before datapoints and 101,459 after
datapoints. Analyzing this dataset it was found that
average speed increased slightly while, 50th percentile
speed, 85th percentile speed, and 95th percentile speed all
remained unchanged from before to after “20 is Plenty.”
There was a slight increase in the number and percent of
vehicles traveling over 30 mph and 35 mph from before to
after “20 is Plenty” (see Table 1).
Table 1. Comparison of Summary Statistics for Combined Dataset of Before and After Count Locations
Before Average After Average Change (value)Change (percent)
Average Speed (mph)21.57 21.90 0.33 +1.54%
50th percentile speed (mph)22 22 0 0%
85th percentile speed (mph)27 27 0 0%
95th percentile speed (mph)30 30 0 0%
Percent of Vehicles
Traveling Below 20 mph 39.21%33.33%-5.88%
Percent of Vehicles
Traveling Above 30 mph 3.43%5.42%+1.99%-
Percent of Vehicles
Traveling Above 35 mph 0.37%0.83%+0.46%-
The City of Boulder also collected traffic count and speed data at ten additional locations only after
“20 is Plenty.” These ten additional locations add 45,429 datapoints to the dataset of 101,459 after
counts in the before/after analysis to create a dataset with 146,888 datapoints. Combining these two
datasets must consider that this removes a direct one-to-one correlation between before and after locations, however,
increasing the sample size improves the robustness of the summary statistics and provides an additional reference point.
Adding in the additional ten “after-only” locations only minimally changes the before/after results, showing a smaller
increase in the percent of vehicles traveling above 30 mph and 35 mph compared to the before/after results (see Table 2).
Table 2. Comparison of Summary Statistics for Combined Dataset of Before and After Count Locations,
including "After-Only" count locations
Before Average After Average Change (value)Change (percent)
Average Speed (mph)21.57 21.92 0.35 1.62%
50th percentile speed (mph)22 22 0 0%
85th percentile speed (mph)27 27 0 0%
95th percentile speed (mph)30 30 0 0%
Percent of Vehicles
Traveling Below 20 mph 39.21%33.15%-6.06%
Percent of Vehicles
Traveling Above 30 mph 3.43%4.91%+1.48%-
Percent of Vehicles
Traveling Above 35 mph 0.37%0.65%+0.28%-
The City found that,
overall, vehicle
speeds on local
streets did not
measurably change
after implementing
“20 is Plenty”.
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Evaluation of 20 IS PLENTY Summary Report
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The project team collected roadway characteristic information for each location studied. These characteristics included:
•Street Width
•Travel Lane Width
•Presence of Posted Speed Limit Sign
•Presence and Number of Parking Lanes
•Parking Lane Width
•Typical On-Street Parking Density
•Presence of Striped Centerline
•Presence and Type of Bicycle Facility
(Neighborhood GreenStreet)
•Presence and Type of Sidewalk
•Average Number of Driveways and Access Points
•Approximate Level of Tree Canopy
•Street Segment Intersection Density
•Distance Between Traffic Control Devices
•Types of Traffic Control Devices
•Presence of Crosswalks
•Presence of Raised Crosswalks
Overall, although locations with before/after speed reductions did not point to strong connections to roadway
characteristics, the existence of posted speed limit signs, striped street centerlines, and existing Neighborhood
GreenStreet classifications were most frequently correlated with reductions in speeds from before and after “20 is
Plenty” was put into effect.
Hypothesis Testing
Statistical hypothesis testing was conducted for each of the 22 before and after speed locations to see if the average
speeds decreased (with 95% statistical confidence) after the speed limit was lowered from 25 mph to 20 mph. Though
on average there were minimal changes in vehicle speeds from before to after “20 is Plenty,” the results varied by
location. After “20 is Plenty,” average speed decreased in 17 directions and increased in 27 directions. More specifically,
average speed decreased in both directions of travel at 4 locations, decreased in one direction of travel at 9 locations,
increased in one direction of travel at 9 locations increased in both directions of travel at 9 locations and did not change
in one direction of travel (see Table 3). These results, coupled with the minimal changes in average, 50th percentile, 85th
percentile, and 95th percentile speeds, indicate small changes in speeds at individual locations but no substantial changes
in vehicle speeds citywide.
Table 3. Compiled Summary Statistics for Before and After Count Locations
Summary Statistics Decrease Increase No Change
Average Speed Number of directional count locations 17 27 -
Percentage 39%61%-
50th Percentile Speed Number of directional count locations 20 24 -
Percentage 45%55%-
85th Percentile Speed Number of directional count locations 21 23 -
Percentage 48%52%-
95th Percentile Speed Number of directional count locations 21 22 1
Percentage 48%50%2%
Drivers Traveling 10 mph
Above Speed Limit
Number of directional count locations 13 20 -
Percentage 39%61%-
Drivers Traveling 15 mph
Above Speed Limit
Number of directional count locations 8 14 -
Percentage 36%64%-
Linear Regression – After Data Only
A linear regression analysis was performed on the locations with after only data to determine to what extent various
roadway characteristics could be attributed to reduced vehicle speeds. The after data only was used for this analysis
since it was a larger set of data, and the intent was to relate how motorists were driving after the change to 20 mph
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to roadway characteristics. The regression analysis
determined whether any linear relationship existed
between average speeds and roadway characteristics,
such as street width, lane width, presence of striped
centerline, presence of speed limit sign, parking density,
etc. The results of the linear regression analysis suggest
that narrower streets/lanes and the absence of a striped
centerline correlate with lower average speeds.
Photo Radar Van Data Analysis
The city currently uses photo radar vans to enforce speed limits on local streets. The van is moved around to different
locations with identified speeding issues. In the “20 is Plenty” evaluation, six directional locations of deployment of
the photo radar van including 911 hours of before deployment and 699 hours of after deployment showed an average
reduction of average vehicle speeds of 2.1 mph from 25.6 mph before “20 is Plenty” to 23.5 mph after “20 is Plenty.”
However, because the speed limit was reduced from 25 to 20 mph the number of violations per hour in these 6 locations
went up from 2.5 per hour to 8.4 per hour (see Table 4).
Table 4. Photo Van Radar Before/After Summary Statistics
Average of Average Overall Speed Violations Per Hour
Location Before After Change Before After Change
2400 9th St Northbound 22.6 22.2 -0.4 4.2 3.1 -1.1
3200 Aurora Ave Westbound 25.5 24.0 -1.5 2.0 9.1 +7.1
1200 Block Bear Mountain Dr Eastbound 25.6 22.3 -3.2 1.2 2.8 +1.7
1100 Block Bear Mountain Dr Eastbound 25.8 23.4 -2.4 1.0 6.6 +5.6
2200 Spruce St Westbound 27.1 24.5 -2.6 4.8 11.6 +6.9
2200 Spruce St Eastbound 27.2 24.9 -2.3 5.2 16.2 +11.1
Average of Before/After Locations 25.6 23.5 -2.1 2.5 8.4 +5.9
In two locations, after “20 is Plenty” pneumatic tube counter data was also collected – though on different months than
the photo enforcement data. In these two instances the average after speeds recorded by the photo radar van were 1
mph slower than the after speeds recorded by pneumatic counters. The sample size of the pneumatic counter dataset
was 8,991 vehicle counts while the sample size of the photo radar van dataset was 20,315 vehicle counts. Additionally,
one of these locations included before “20 is Plenty” data which showed almost no difference (+0.01) between the
pneumatic counter and photo radar van measured speeds (n=5,262 for pneumatic, n=43,813 for photo radar van).
Table 5. Comparison of Pneumatic Tube Data and Photo Radar Van Data Before and After "20 is Plenty"
Pneumatic Tube Data Photo Radar Van Data Average Speed
ComparisonAverage of Average
Overall Speed Sample Size Average of Average
Overall Speed Sample Size
Location Before After Before After Before After Before After Before After
3200 Aurora Ave
Westbound 25.49 25.03 5,262 3,420 25.50 23.98 43,813 6,538 +0.01 -1.05
1200 Eisenhower
Dr Northbound n/a 23.06 n/a 5,571 n/a 22.12 n/a 13,777 n/a -0.94
While this is a limited subset of the overall citywide dataset, it suggests that the presence of the photo radar van may
have influenced vehicle speeds more after “20 is Plenty” was enacted in Boulder than it did before “20 is Plenty”,
though further analysis in more locations would be needed to confirm this hypothesis.
The City found that local streets with lower vehicle
speeds tend to have narrower widths, narrower
lanes, and no striped centerline. Additionally,
Neighborhood GreenStreets were more likely to
have lower vehicle speeds.
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Before and After 85th Percentile Speeds by Location
The before and after “20 is Plenty” 85th percentile speeds and change in 85th percentile
speeds by count location are shown on the following pages in Figures 3-6. The before
85th percentile speeds ranged from 16 mph to 31 mph. The after 85th percentile speeds
ranged from 20 mph to 34 mph (Figure 1). The change in 85th percentile speeds ranged
from a reduction of 4 mph to an increase of 4 mph (Figure 2). The maps in Figures 3
through 6 show how results varied by location. Further study of individual locations
could reveal insights into why speeds were reduced or increased.
The 85th percentile speed
is the speed at or below
which 85 percent of
vehicles drive, and it is
a common metric for
assessing speeds on streets.
Nearly all streets studied in both the before and after conditions
had 85th percentile vehicle speeds well over the 20 mph speed limit,
and a substantial number more than 25 mph.
1 2 3 4 5 6Key:
After “20
is Plenty”
Before “20
is Plenty”
mph
15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35
Figure 1: 85th Percentile Speeds By Location
Figure 2: Change in 85th Percentile Speeds By Location
-5 -4 -3 -2 -1 0 1 2 3 4 5
mph
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Figure 3: Locations of before and after traffic count data collection
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Figure 4: Average 85th Percentile Speed Before “20 is Plenty” Initiative
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Figure 5: Average 85th Percentile Speed After “20 is Plenty” Initiative
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Figure 6: Change in 85th Percentile Speed from Before to After “20 is Plenty” Initiative
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Relevant Guidance and Peer City Efforts
1 NTSB, Reducing Speeding-Related Crashes Involving Passenger Vehicles. 2017. P. ix.
2 NTSB, Reducing Speeding-Related Crashes Involving Passenger Vehicles. 2017
3 NACTO, Cairns et al. City Limits: Setting Safe Speed Limits on Urban Streets, 2020, p. 50
Literature Review
Relevant research and guidance documents on the topics
of reducing local speeds and reducing speeding-related
crashes were summarized to understand national and
international best-practices in speed limit reduction. The
following research and guidance reports were studied:
•NCHRP 966: Posted Speed Limit Setting Procedure
and Tool: User Guide
•NTSB Reducing Speeding-Related Crashes Involving
Passenger Vehicles
•FHWA Methods and Practices for Setting Speed
Limits
•FHWA Speed Management Toolkit
•NACTO City Limits: Setting Safe Speed Limits on
Urban Streets
•GHSA Speeding Away from Zero: Rethinking a
Forgotten Traffic Safety Challenge
•Transport for London Achieving lower speeds: the
toolkit
Results of these studies supported final recommendations
and are important for better understanding the proven
benefits of speed reductions and generating ideas for
additional engineering, enforcement, and education
strategies for reducing speeds.
Reducing Speeds to 20 mph
When drivers speed it increases the likelihood of a crash
occurring and the severity of injuries that can result
from a crash for all roadway users, but especially for
vulnerable road users including people walking and
bicycling. The National Transportation Safety Board (NTSB)
Reducing Speeding-Related Crashes Involving Passenger
Vehicles study concluded that 31% of all crashes resulting
in fatalities within the study data were speeding-
related.1 20 mph is considered the survivability speed for
pedestrians and bicyclists when involved in a crash with a
vehicle. In the event of a crash involving a pedestrian, the
probability of that crash being fatal “increases from 5%
at a vehicle impact speed of 20 mph, to 45% at 30 mph,
and 85% at 40 mph.”2 The Federal Highway Administration
(FHWA) Methods and Practices for Setting Speed Limits and
the National Association of City Transportation Officials
(NACTO) City Limits: Setting Safe Speed Limits on Urban
Streets similarly conclude that minor streets with a mix
of motor vehicles, pedestrians, and cyclists should be
have 20 mph speed limits to “support safe movement and
contextually appropriate design on the majority of city
streets.”3
Reducing speeds to 20 mph is a best practice for keeping
vulnerable road users safe on local streets. Transport
for London’s Achieving lower speeds: the toolkit describes
a similar “blanket” approach that Boulder has used to
implement 20 mph speed limits on local streets. Transport
for London found that setting a 20 mph prima facie
speed limit enabled local government to implement 20
mph limits more easily and confidently on other higher
classification streets outside of residential areas.
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Successful Speed Management Programs
The FHWA Speed Management Toolkit and Governors
Highway Safety Association (GHSA) Speeding Away
from Zero report provide similar guidance for improving
programs and policies to support speed reductions. To
implement successful speed management projects, these
two guidance documents advise local agencies to:
1. Build a platform and improve program management
by assigning roles and responsibilities to state and
local task forces or advisory committees and keeping
leaders regularly updated.
2. Improve state and local policy by encouraging
infrastructure and enforcement improvements and
promoting Vision Zero principles.
3. Communicate with community members by using
several types of media to deliver consistent
messaging.
4. Identify and deploy a Culture Change Model that
changes driver-perception that speeding is a low-
risk activity by localizing messaging and building a
coalition of supporters and partners.
Several strategies to improve active speed management
programming found in reviewed literature align with
strategies Boulder has already deployed or tools
considered in this “20 is Plenty” evaluation. In the
Speeding Away from Zero report, the GHSA recommends
implementing speed management programs in
conjunction with Vision Zero that focus on education,
enforcement, and infrastructure. Emphasizing awareness,
community partnerships, and culture change is also a
relatively consistent theme across all literature. The
City of Boulder is already implementing many of these
strategies through robust, ongoing Vision Zero work.
Peer City Interview Key Findings
Interviews with staff from four peer cities were
conducted to provide additional insights into
recommendations for speed limit reductions in Boulder.
The cities included Portland, Oregon; Eugene, Oregon;
Cambridge, Massachusetts; and Seattle, Washington.
Some similarities between the approach to speed limit
reductions in these cities are:
•All cities interviewed have reduced speed limits on
most or all local streets from 25 mph to 20 mph
•In additional to reducing speed limits on local streets,
Portland, Cambridge, and Seattle have reduced
speed limits on arterial streets (typically in 5 mph
increments from before conditions of 25, 30, or 35
mph to after conditions of 20, 25, or 30 mph)
•In addition to reducing speed limits, Portland and
Seattle also conducted evaluations of their speed
limit reductions.
Below is a summary of key takeaways from the peer city
interviews organized by topic.
Communication
All cities, excluding Seattle, performed some type
and degree of marketing and advertising campaigns
surrounding local street speed limit reduction. Press
conferences, radio and print campaigns, and social media
posts were most common. City staff agreed that the most
consistent and successful method for communicating
speed limit changes was the large-scale distribution
of yard signs. Peer cities also raised awareness by
collaborating with neighborhood groups, interested
residents, and local organizations and programs including
Safe Routes to School.
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School Zones and Posted Signage
None of the peer cities interview have further reduced
school zone speed limits to 15 mph after implementing
speed limit reductions to 20 mph on local streets, largely
because of the state government’s level of control
over speed limit setting in Oregon, Washington, and
Massachusetts. The City of Seattle removed the majority
of old advisory speed signs that conflicted with newly
posted 20 and 25 mph signs. Multiple municipalities noted
that speed limit reductions revealed the need for a higher
frequency of posted signage, especially on local streets
adjacent to higher-traffic streets, and the need to improve
consistency in the placement of speed limit signs.
Evaluation Process
The City of Portland and the City of Seattle are the only
interviewed cities that completed before and after data
analysis of vehicle speeds. Of note, both cities’ studies
had constraints like Boulder’s evaluation in that there was
relatively limited before/after data on which conclusions
could be drawn. In addition, it does not appear that these
cities accounted for the error (typically ± 1 mph) of their
traffic counters when presenting results.
Portland evaluated speeds before and after the reduction
of the local street speed limit from 25 mph to 20 mph in
58 locations and found:
•No change in median speed or 85th percentile speed
•Very small reductions in the percent of drivers
traveling greater than 25 (-0.5%), 30 (-1.7%), and 35
(-0.5%) mph
Seattle evaluated speeds before and after spot reductions
of the speed limit on arterials in North Seattle from 30
mph to 25 mph and found:
•Reductions in crashes (-22% for total crashes, -18%
for injury crashes)
•Reductions in 50th percentile (-9.9%), 85th percentile
speeds (-7.1%), and the percent of drivers traveling
40 mph or greater (-54.1%)
4 NACTO, Cairns et al. City Limits: Setting Safe Speed Limits on Urban Streets, 2020, p. 18
Updated Methods and Design Programs for Setting and
Reinforcing Lower Speed Limits
While design standards and methods for setting speed
limits were not significantly affected, cities found that
implementing lower speed limits revealed a need to
retrofit streets with traffic calming to reinforce the
lower speed limits. Peer cities noted that the speed limit
reductions led to a procedural shift where staff now
design streets for target speeds rather than the 85th
percentile speed, which studies have shown can lead to
increases in vehicle speeds over time.4 The speed limit
reductions also led staff to revise speed management
programs to be more context sensitive and increased the
number of streets eligible for traffic calming projects.
Enforcement
The four cities use a combination of automated
enforcement (fixed cameras and photo radar vans),
speed feedback trailers, and fixed speed radar signs
to encourage or enforce the speed limit. Many cities
expressed that enforcement is typically a short-term
solution when areas pop up as speeding hotspots either
through resident complaints, staff speed studies and/
or staff crash analysis. Cities favored an engineering
approach that redesigns streets to bring speeds down
permanently through traffic calming infrastructure
changes rather than using enforcement on an ongoing
basis.
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Recommendations
Below are recommendations for introducing or modifying speed management programs,
policies, procedures, and projects in the City of Boulder to align with “20 is Plenty.”
Topic Number
4E
Approach
Correlation
Recommendation Justification
Neighborhood
Speed
Management
Program
1
Update NSMP engineering
toolkit to include the removal of
striped centerline markings and
treatments that provide a mix of
horizontal and vertical deflection;
review guidelines and industry
best practices for speed hump
placement along streets with 20
mph speed limits.
Streets with narrower curb to curb
widths, narrower vehicle travel
lanes, and no striped centerline
are more likely to have lower
speeds. Currently, the NSMP toolkit
of engineering solutions does not
include striped centerline removal
or parklets as means to narrow
street widths. While speed humps
are included as a tool, speed hump
frequency is not defined. The
evaluation of “20 is Plenty” did not
include locations with speed humps,
but speed humps have been proven
to lower maximum speeds if spaced
appropriately.
2
Launch data-driven speed
management program
focused solely on arterial
streets, involving community
engagement instead of accepting
resident applications.
NSMP criteria allows for only local
or collector streets to be submitted
and considered for improvements,
but 65% of severe crashes occur
on arterial roads, 11% occur on
collectors, and 11% occur on local
streets in Boulder.
3
Prioritize segments of local
streets that adjoin arterial
streets.
Alongside recommendation
2, Boulder would benefit from
prioritizing traffic calming at arterial
and residential street junctions
and residential gateways adjoining
arterial streets.
Key:
Engineering Evaluation Enforcement Education
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Topic Number
4E
Approach
Correlation
Recommendation Justification
Designing for
Target Speeds
4
Revise the Design and
Construction Standards to use a
20 mph target speed for local
street design.
The City of Boulder’s current
engineering approach to designing
streets includes looking at the
speeds that 85% of motorists are
driving (85th percentile speeds) and
designing to accommodate these
speeds. In contrast, cities using
the safe system approach decide
what speed is safest to travel on a
given street and design the street
so the majority of people will drive
that target speed. Adjusting design
standards to match target speeds
(50th percentile speeds) has proven
to be successful.
5
Conduct a systematic evaluation
of existing local street widths
(and speed-related crashes) to
identify segments of concern;
prioritize segments of concern
for inclusion in future traffic
calming projects or programs
such as the NSMP.
The standard cross-section for
a residential street is a two-way
street with 30 feet of space curb
face to curb face with on-street
parking permitted. With two on-
street parking lanes of 8 feet each
this equates to 14 feet of travelled
way between parked cars. This
standard is best practice for keeping
speeds low, but some residential
streets in Boulder exceed these
widths.
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Topic Number
4E
Approach
Correlation
Recommendation Justification
Functional
Street
Classifications
6
Identify street segments
currently classified as local
streets that function as higher
classification roads.
Some streets currently classified as
Local may be a better classified as a
Collector or as somewhere between
a Local and Collector as outlined in
the next recommendation.
7
Consider reclassifying select
streets/street segments from
local to collector where the
access density, transit stop
density, emergency response
route, snowplow route, and other
characteristics relate more
closely to other streets with
higher classifications.
There are some streets currently
classified as Local streets that
serve a higher volume of traffic,
connect directly to more community
destinations, and in many cases
are wider and have a striped
centerline. Oftentimes there is a
school on these local streets. For
these streets, it may be better to
use a new street classification if the
street is a key connection for area
residents rather than a primarily
residential street.
8
Consider developing an Industrial
Street and Business Park Street
classification to better match
streets providing access to
industrial and business land
uses.
Some streets currently classified
as Local streets do not have any
adjacent residences and serve light
industrial or business uses. Because
of this context they are designed
more for large truck access.
Rather than redesigning them with
treatments more appropriate for
residential streets, a reclassification
may be a better approach –
matching their classification to the
existing design.
9
Evaluate speed limit reductions
along high-crash, high-speed
arterial corridors using the
speed limit setting framework
that will be developed in the
upcoming Community Mobility
Planning and Implementation
(CMPI) Speed Limit Setting and
Signing Framework grant project.
Arterial streets comprise 17% street
centerline miles in Boulder but
account for 65% of severe crashes.
Focusing speed reduction efforts
on key arterial street segments will
have a greater effect than focusing
only on local and collector streets.
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Topic Number
4E
Approach
Correlation
Recommendation Justification
Additional
Speed Limit
Reductions to
Support Vision
Zero
10
Prioritize arterial speed limit
reductions on high-stress
arterial corridors that also
adjoin local streets where 20
mph speed limits have been
introduced.
Some arterial streets may be
better candidates for speed limit
reductions if they are adjacent to
primarily residential land uses
where the speed limits have already
been reduced.
Speed Limit
Setting in
School Zones
11
Consider reducing speed limits
in select school zones from
20 mph to 15 mph based the
school circulation patterns, sight
distance, roadway width, nearby
land uses and other various
criteria.
The potential for a severe crash
outcome for someone walking
or bicycling is lower at 20 mph
than at 30 or 40 mph, however,
the risk is higher for children
than adults. Therefore, in some
school zone locations (especially
near elementary schools) a 15
mph speed limit may be more
appropriate to reduce the risk to
children walking and bicycling.
12
Working with partners at the
Boulder Valley School District,
identify potential locations where
School Streets (shared streets
in front of schools) could be
implemented to best support
speed reductions and encourage
mode shift.
School Streets can help encourage
walking and bicycling to school
and reduce the complexity of
interactions and potential conflicts
between students and caregivers
walking, bicycling, or driving in the
street immediately adjacent to the
school.
Standardizing
Signage 13
Through the CMPI Speed Limit
Setting and Signing Framework
grant, develop a consistent
practice for installing 20 mph
speed limit signs on local streets
and at additional key gateway
locations throughout the city.
There was a slight correlation
between streets with posted speed
limit signs and speed reductions.
Adding more speed limit signs
systematically in key locations may
assist in system-wide local street
travel speed reductions.
Warning Signs/
Advisory
Speeds
14 No Change Needed N/A
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Topic Number
4E
Approach
Correlation
Recommendation Justification
Photo Radar Van
Program and
Radar Speed
Signs
15
Periodically re-evaluate the
location of street segments on
which to deploy the photo radar
vans.
These locations are where average
vehicle speeds were the highest
and 95th percentile vehicle speeds
(excessive speeding) increased the
most in the evaluation. They may
be good candidates for targeted
enforcement as a short-term
solution while street redesigns or
other speed reduction measures are
considered.
16
Consider lobbying members
of the Colorado General
Assembly to allow automated
enforcement on arterial streets.
Vehicle speeds are higher on
arterial streets than on local streets,
however, Colorado Revised Statutes
currently only allow automated
enforcement on streets in school
zones, residential neighborhoods,
within a maintenance, construction,
or repair zone, and along streets
that border a municipal park. While
some of these conditions overlap
arterial streets, many do not.
Allowing automated enforcement on
more arterial streets can assist the
city in reducing speeds citywide in
the short-term.
17
Expand the use of both
permanent and portable radar
speed feedback signs along
arterial streets.
NSMP projects focus on local and
collector streets. Radar speed signs
could also be effective in reducing
speeds on arterial streets.
Pedestrian
Crossing
Treatment
Installation
Guidelines
18 No change needed N/A
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Topic Number
4E
Approach
Correlation
Recommendation Justification
Promotion and
Engagement
19
Increase the presence of “20 is
Plenty” yard signs and update
messaging to incorporate
statistics on speeding crashes,
speed enforcement, and
community disapproval of
speeding.
Through ongoing review of data
and coordination with the police
department, target the expansion
of photo radar van deployment to
areas with highest speeds.
20
Reintroduce other “20 is Plenty”
advertising including media
and online efforts to spread
awareness of Vision Zero.
Better understanding of the
new speed limit and reasons for
reducing it could help more people
driving comply with the speed limit.
21
Develop a Culture Change Model
approach that changes social
perceptions of the risks of
speeding.
Many communities conduct
educational campaigns that
humanize the victims of traffic
crashes which helps communicate
the negative consequences that can
occur because of speeding.
22
Communicate and collaborate
with local organizations and
existing programs like Safe
Routes to School to create and
promote campaigns specifically
focused on drivers who speed
A multi-pronged communications
approach describing different
reasons why “20 is Plenty” is
important will appeal to a broader
audience.
23 Extend speeding education to
reach beyond NSMP project sites.
The NSMP has great existing
promotional materials that could be
expanded for use on other projects
outside of NSMP streets.
Next Steps
Despite the results of the evaluation, local streets generally continue to not exhibit speed-related crash patterns, as
indicated in the Draft Safe Streets Report, 4th Edition 2022. Thus, the recommendations presented will need to be
balanced against priorities and implemented over time as part of a comprehensive Vision Zero strategy.
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20 IS PLENTY
Summary Report
Evaluation of
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This report is provided for informational purposes only, and all results, recommendations, and commentary contained herein are based
on limited data available at the time of preparation. Further planning and policy analysis may be necessary prior to implementing the
recommendations contained herein. Toole Design makes no representations or warranties regarding the accuracy of the underlying source data.
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Contents
What is “20 is Plenty?” ................................................2
Purpose, Goals, and Key Performance Indicators ....2
Purpose ..........................................................................................................2
Goals ...............................................................................................................2
Key Performance Indicators .......................................................................2
Evaluation Method and Results ..................................3
Comparing Key Performance Indicators ..................................................3
Hypothesis Testing .......................................................................................4
Linear Regression – After Data Only ........................................................4
Photo Radar Van Data Analysis..................................................................5
Before and After 85th Percentile Speeds by Location ............................6
Relevant Guidance and Peer City Efforts .................11
Literature Review ......................................................................................11
Reducing Speeds to 20 mph ...........................................................................11
Successful Speed Management Programs ..................................................12
Peer City Interview Key Findings ............................................................12
Communication .................................................................................................12
School Zones and Posted Signage ................................................................13
Evaluation Process ...........................................................................................13
Updated Methods and Design Programs for Setting and
Reinforcing Lower Speed Limits ....................................................................13
Enforcement ......................................................................................................13
Recommendations .....................................................14
Next Steps ..................................................................19
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What is “20 is Plenty?”
Across the United States and other countries, there is
an emphasis on lowering speed limits in an effort to
reduce the potential for serious injuries when crashes
occur and to improve the livability of local streets. This
initiative is commonly referred to as “20 is Plenty.” In June
2020, the City of Boulder committed to “20 is Plenty.” City
Council passed an ordinance to lower the prima facie
(also known as default or unposted) speed limit from 25
mph to 20 mph. Concurrent with the ordinance passage,
staff changed a total of approximately 465 speed limit
signs from 25 mph to 20 mph signs on local streets,
where applicable, and updated the “Welcome to Boulder”
gateway signs at the city limits to indicate the citywide 20
mph default speed limit.
The city views “20 is Plenty” as one aspect of its
commitment to achieving Vision Zero, which is the city’s
goal to reduce the number of traffic-related fatalities and
serious injuries to zero. As such, the new 20 mph speed
limit signs include an orange outline and the words “Vision
Zero” across the top of the sign to remind motorists of the
connection of slower speeds to reduced severe crashes.
Evidence suggests there is a greater chance for pedestrian
and bicyclist survival when vehicles are traveling 20 mph
compared to vehicles traveling at higher speeds. Slower
travel speeds on locally-classified residential streets also
increase the likelihood of people driving yielding to people
walking and bicycling and contribute to a more comfortable
environment for people to walk and bicycle.
Purpose, Goals, and Key
Performance Indicators
Purpose
The purpose of this evaluation is to study whether
lowering the speed limit and changing posted speeds
from 25 mph to 20 mph on local streets resulted in
reduced vehicle speeds. The evaluation also provides
recommendations to introduce or modify speed
management programs, procedures, and policies to align
with the new 20 mph speed limit.
Goals
The evaluation had three main goals:
1. To study other cities who have implemented “20
is Plenty” to understand results achieved and
impacts to projects and programs.
2. To evaluate the City of Boulder’s implementation
of “20 is Plenty,” focusing on whether it has
resulted in reduced vehicle speeds.
3. To understand how “20 is Plenty” has affected
existing projects and programs in the city and
formulate recommendations for changes or
enhancements.
Key Performance Indicators
To measure the success of reducing the prima facie speed
limit from 25 mph to 20mph on local streets, before and
after vehicle speed data from 22 locations across the city
was analyzed. This evaluation focused on the following
key performance indicators:
•Percent and number of drivers traveling at
or below 20 mph
•Percent change in mean (average) speed
•Percent change in median (50th percentile) speed
•Percent change and number of drivers traveling
10 mph over the (new) speed limit
•Percent change and number of drivers traveling
15 mph over the (new) speed limit
•Percent change in 85th percentile speed
•Percent change in 95th percentile speed
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Evaluation Method and Results
The evaluation of “20 is Plenty” used vehicle speed data
collected at 22 locations before and after the speed limit
reduction, 10 additional locations with data collected
only after the speed limit reduction, and 6 locations with
photo speed van radar data collected before and after the
speed limit reduction. In each case, the streets were two-
way streets, so data was separated into two directions
of travel. The analysis was organized into three parts:
comparing key performance indicators, hypothesis testing,
and linear regression.
Comparing Key Performance Indicators
Combining all 22 locations with before and after speed
count data to create one citywide dataset created a
dataset of 140,454 before datapoints and 101,459 after
datapoints. Analyzing this dataset it was found that
average speed increased slightly while, 50th percentile
speed, 85th percentile speed, and 95th percentile speed all
remained unchanged from before to after “20 is Plenty.”
There was a slight increase in the number and percent of
vehicles traveling over 30 mph and 35 mph from before to
after “20 is Plenty” (see Table 1).
Table 1. Comparison of Summary Statistics for Combined Dataset of Before and After Count Locations
Before Average After Average Change (value)Change (percent)
Average Speed (mph)21.57 21.90 0.33 +1.54%
50th percentile speed (mph)22 22 0 0%
85th percentile speed (mph)27 27 0 0%
95th percentile speed (mph)30 30 0 0%
Percent of Vehicles
Traveling Below 20 mph 39.21%33.33%-5.88%
Percent of Vehicles
Traveling Above 30 mph 3.43%5.42%+1.99%-
Percent of Vehicles
Traveling Above 35 mph 0.37%0.83%+0.46%-
The City of Boulder also collected traffic count and speed data at ten additional locations only after
“20 is Plenty.” These ten additional locations add 45,429 datapoints to the dataset of 101,459 after
counts in the before/after analysis to create a dataset with 146,888 datapoints. Combining these two
datasets must consider that this removes a direct one-to-one correlation between before and after locations, however,
increasing the sample size improves the robustness of the summary statistics and provides an additional reference point.
Adding in the additional ten “after-only” locations only minimally changes the before/after results, showing a smaller
increase in the percent of vehicles traveling above 30 mph and 35 mph compared to the before/after results (see Table 2).
Table 2. Comparison of Summary Statistics for Combined Dataset of Before and After Count Locations,
including "After-Only" count locations
Before Average After Average Change (value)Change (percent)
Average Speed (mph)21.57 21.92 0.35 1.62%
50th percentile speed (mph)22 22 0 0%
85th percentile speed (mph)27 27 0 0%
95th percentile speed (mph)30 30 0 0%
Percent of Vehicles
Traveling Below 20 mph 39.21%33.15%-6.06%
Percent of Vehicles
Traveling Above 30 mph 3.43%4.91%+1.48%-
Percent of Vehicles
Traveling Above 35 mph 0.37%0.65%+0.28%-
The City found that,
overall, vehicle
speeds on local
streets did not
measurably change
after implementing
“20 is Plenty”.
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The project team collected roadway characteristic information for each location studied. These characteristics included:
•Street Width
•Travel Lane Width
•Presence of Posted Speed Limit Sign
•Presence and Number of Parking Lanes
•Parking Lane Width
•Typical On-Street Parking Density
•Presence of Striped Centerline
•Presence and Type of Bicycle Facility
(Neighborhood GreenStreet)
•Presence and Type of Sidewalk
•Average Number of Driveways and Access Points
•Approximate Level of Tree Canopy
•Street Segment Intersection Density
•Distance Between Traffic Control Devices
•Types of Traffic Control Devices
•Presence of Crosswalks
•Presence of Raised Crosswalks
Overall, although locations with before/after speed reductions did not point to strong connections to roadway
characteristics, the existence of posted speed limit signs, striped street centerlines, and existing Neighborhood
GreenStreet classifications were most frequently correlated with reductions in speeds from before and after “20 is
Plenty” was put into effect.
Hypothesis Testing
Statistical hypothesis testing was conducted for each of the 22 before and after speed locations to see if the average
speeds decreased (with 95% statistical confidence) after the speed limit was lowered from 25 mph to 20 mph. Though
on average there were minimal changes in vehicle speeds from before to after “20 is Plenty,” the results varied by
location. After “20 is Plenty,” average speed decreased in 17 directions and increased in 27 directions. More specifically,
average speed decreased in both directions of travel at 4 locations, decreased in one direction of travel at 9 locations,
increased in one direction of travel at 9 locations increased in both directions of travel at 9 locations and did not change
in one direction of travel (see Table 3). These results, coupled with the minimal changes in average, 50th percentile, 85th
percentile, and 95th percentile speeds, indicate small changes in speeds at individual locations but no substantial changes
in vehicle speeds citywide.
Table 3. Compiled Summary Statistics for Before and After Count Locations
Summary Statistics Decrease Increase No Change
Average Speed Number of directional count locations 17 27 -
Percentage 39%61%-
50th Percentile Speed Number of directional count locations 20 24 -
Percentage 45%55%-
85th Percentile Speed Number of directional count locations 21 23 -
Percentage 48%52%-
95th Percentile Speed Number of directional count locations 21 22 1
Percentage 48%50%2%
Drivers Traveling 10 mph
Above Speed Limit
Number of directional count locations 13 20 -
Percentage 39%61%-
Drivers Traveling 15 mph
Above Speed Limit
Number of directional count locations 8 14 -
Percentage 36%64%-
Linear Regression – After Data Only
A linear regression analysis was performed on the locations with after only data to determine to what extent various
roadway characteristics could be attributed to reduced vehicle speeds. The after data only was used for this analysis
since it was a larger set of data, and the intent was to relate how motorists were driving after the change to 20 mph
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to roadway characteristics. The regression analysis
determined whether any linear relationship existed
between average speeds and roadway characteristics,
such as street width, lane width, presence of striped
centerline, presence of speed limit sign, parking density,
etc. The results of the linear regression analysis suggest
that narrower streets/lanes and the absence of a striped
centerline correlate with lower average speeds.
Photo Radar Van Data Analysis
The city currently uses photo radar vans to enforce speed limits on local streets. The van is moved around to different
locations with identified speeding issues. In the “20 is Plenty” evaluation, six directional locations of deployment of
the photo radar van including 911 hours of before deployment and 699 hours of after deployment showed an average
reduction of average vehicle speeds of 2.1 mph from 25.6 mph before “20 is Plenty” to 23.5 mph after “20 is Plenty.”
However, because the speed limit was reduced from 25 to 20 mph the number of violations per hour in these 6 locations
went up from 2.5 per hour to 8.4 per hour (see Table 4).
Table 4. Photo Van Radar Before/After Summary Statistics
Average of Average Overall Speed Violations Per Hour
Location Before After Change Before After Change
2400 9th St Northbound 22.6 22.2 -0.4 4.2 3.1 -1.1
3200 Aurora Ave Westbound 25.5 24.0 -1.5 2.0 9.1 +7.1
1200 Block Bear Mountain Dr Eastbound 25.6 22.3 -3.2 1.2 2.8 +1.7
1100 Block Bear Mountain Dr Eastbound 25.8 23.4 -2.4 1.0 6.6 +5.6
2200 Spruce St Westbound 27.1 24.5 -2.6 4.8 11.6 +6.9
2200 Spruce St Eastbound 27.2 24.9 -2.3 5.2 16.2 +11.1
Average of Before/After Locations 25.6 23.5 -2.1 2.5 8.4 +5.9
In two locations, after “20 is Plenty” pneumatic tube counter data was also collected – though on different months than
the photo enforcement data. In these two instances the average after speeds recorded by the photo radar van were 1
mph slower than the after speeds recorded by pneumatic counters. The sample size of the pneumatic counter dataset
was 8,991 vehicle counts while the sample size of the photo radar van dataset was 20,315 vehicle counts. Additionally,
one of these locations included before “20 is Plenty” data which showed almost no difference (+0.01) between the
pneumatic counter and photo radar van measured speeds (n=5,262 for pneumatic, n=43,813 for photo radar van).
Table 5. Comparison of Pneumatic Tube Data and Photo Radar Van Data Before and After "20 is Plenty"
Pneumatic Tube Data Photo Radar Van Data Average Speed
ComparisonAverage of Average
Overall Speed Sample Size Average of Average
Overall Speed Sample Size
Location Before After Before After Before After Before After Before After
3200 Aurora Ave
Westbound 25.49 25.03 5,262 3,420 25.50 23.98 43,813 6,538 +0.01 -1.05
1200 Eisenhower
Dr Northbound n/a 23.06 n/a 5,571 n/a 22.12 n/a 13,777 n/a -0.94
While this is a limited subset of the overall citywide dataset, it suggests that the presence of the photo radar van may
have influenced vehicle speeds more after “20 is Plenty” was enacted in Boulder than it did before “20 is Plenty”,
though further analysis in more locations would be needed to confirm this hypothesis.
The City found that local streets with lower vehicle
speeds tend to have narrower widths, narrower
lanes, and no striped centerline. Additionally,
Neighborhood GreenStreets were more likely to
have lower vehicle speeds.
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Before and After 85th Percentile Speeds by Location
The before and after “20 is Plenty” 85th percentile speeds and change in 85th percentile
speeds by count location are shown on the following pages in Figures 3-6. The before
85th percentile speeds ranged from 16 mph to 31 mph. The after 85th percentile speeds
ranged from 20 mph to 34 mph (Figure 1). The change in 85th percentile speeds ranged
from a reduction of 4 mph to an increase of 4 mph (Figure 2). The maps in Figures 3
through 6 show how results varied by location. Further study of individual locations
could reveal insights into why speeds were reduced or increased.
The 85th percentile speed
is the speed at or below
which 85 percent of
vehicles drive, and it is
a common metric for
assessing speeds on streets.
Nearly all streets studied in both the before and after conditions
had 85th percentile vehicle speeds well over the 20 mph speed limit,
and a substantial number more than 25 mph.
1 2 3 4 5 6Key:
After “20
is Plenty”
Before “20
is Plenty”
mph
15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35
Figure 1: 85th Percentile Speeds By Location
Figure 2: Change in 85th Percentile Speeds By Location
-5 -4 -3 -2 -1 0 1 2 3 4 5
mph
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Figure 3: Locations of before and after traffic count data collection
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Figure 4: Average 85th Percentile Speed Before “20 is Plenty” Initiative
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Figure 5: Average 85th Percentile Speed After “20 is Plenty” Initiative
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Figure 6: Change in 85th Percentile Speed from Before to After “20 is Plenty” Initiative
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Relevant Guidance and Peer City Efforts
1 NTSB, Reducing Speeding-Related Crashes Involving Passenger Vehicles. 2017. P. ix.
2 NTSB, Reducing Speeding-Related Crashes Involving Passenger Vehicles. 2017
3 NACTO, Cairns et al. City Limits: Setting Safe Speed Limits on Urban Streets, 2020, p. 50
Literature Review
Relevant research and guidance documents on the topics
of reducing local speeds and reducing speeding-related
crashes were summarized to understand national and
international best-practices in speed limit reduction. The
following research and guidance reports were studied:
•NCHRP 966: Posted Speed Limit Setting Procedure
and Tool: User Guide
•NTSB Reducing Speeding-Related Crashes Involving
Passenger Vehicles
•FHWA Methods and Practices for Setting Speed
Limits
•FHWA Speed Management Toolkit
•NACTO City Limits: Setting Safe Speed Limits on
Urban Streets
•GHSA Speeding Away from Zero: Rethinking a
Forgotten Traffic Safety Challenge
•Transport for London Achieving lower speeds: the
toolkit
Results of these studies supported final recommendations
and are important for better understanding the proven
benefits of speed reductions and generating ideas for
additional engineering, enforcement, and education
strategies for reducing speeds.
Reducing Speeds to 20 mph
When drivers speed it increases the likelihood of a crash
occurring and the severity of injuries that can result
from a crash for all roadway users, but especially for
vulnerable road users including people walking and
bicycling. The National Transportation Safety Board (NTSB)
Reducing Speeding-Related Crashes Involving Passenger
Vehicles study concluded that 31% of all crashes resulting
in fatalities within the study data were speeding-
related.1 20 mph is considered the survivability speed for
pedestrians and bicyclists when involved in a crash with a
vehicle. In the event of a crash involving a pedestrian, the
probability of that crash being fatal “increases from 5%
at a vehicle impact speed of 20 mph, to 45% at 30 mph,
and 85% at 40 mph.”2 The Federal Highway Administration
(FHWA) Methods and Practices for Setting Speed Limits and
the National Association of City Transportation Officials
(NACTO) City Limits: Setting Safe Speed Limits on Urban
Streets similarly conclude that minor streets with a mix
of motor vehicles, pedestrians, and cyclists should be
have 20 mph speed limits to “support safe movement and
contextually appropriate design on the majority of city
streets.”3
Reducing speeds to 20 mph is a best practice for keeping
vulnerable road users safe on local streets. Transport
for London’s Achieving lower speeds: the toolkit describes
a similar “blanket” approach that Boulder has used to
implement 20 mph speed limits on local streets. Transport
for London found that setting a 20 mph prima facie
speed limit enabled local government to implement 20
mph limits more easily and confidently on other higher
classification streets outside of residential areas.
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Successful Speed Management Programs
The FHWA Speed Management Toolkit and Governors
Highway Safety Association (GHSA) Speeding Away
from Zero report provide similar guidance for improving
programs and policies to support speed reductions. To
implement successful speed management projects, these
two guidance documents advise local agencies to:
1. Build a platform and improve program management
by assigning roles and responsibilities to state and
local task forces or advisory committees and keeping
leaders regularly updated.
2. Improve state and local policy by encouraging
infrastructure and enforcement improvements and
promoting Vision Zero principles.
3. Communicate with community members by using
several types of media to deliver consistent
messaging.
4. Identify and deploy a Culture Change Model that
changes driver-perception that speeding is a low-
risk activity by localizing messaging and building a
coalition of supporters and partners.
Several strategies to improve active speed management
programming found in reviewed literature align with
strategies Boulder has already deployed or tools
considered in this “20 is Plenty” evaluation. In the
Speeding Away from Zero report, the GHSA recommends
implementing speed management programs in
conjunction with Vision Zero that focus on education,
enforcement, and infrastructure. Emphasizing awareness,
community partnerships, and culture change is also a
relatively consistent theme across all literature. The
City of Boulder is already implementing many of these
strategies through robust, ongoing Vision Zero work.
Peer City Interview Key Findings
Interviews with staff from four peer cities were
conducted to provide additional insights into
recommendations for speed limit reductions in Boulder.
The cities included Portland, Oregon; Eugene, Oregon;
Cambridge, Massachusetts; and Seattle, Washington.
Some similarities between the approach to speed limit
reductions in these cities are:
•All cities interviewed have reduced speed limits on
most or all local streets from 25 mph to 20 mph
•In additional to reducing speed limits on local streets,
Portland, Cambridge, and Seattle have reduced
speed limits on arterial streets (typically in 5 mph
increments from before conditions of 25, 30, or 35
mph to after conditions of 20, 25, or 30 mph)
•In addition to reducing speed limits, Portland and
Seattle also conducted evaluations of their speed
limit reductions.
Below is a summary of key takeaways from the peer city
interviews organized by topic.
Communication
All cities, excluding Seattle, performed some type
and degree of marketing and advertising campaigns
surrounding local street speed limit reduction. Press
conferences, radio and print campaigns, and social media
posts were most common. City staff agreed that the most
consistent and successful method for communicating
speed limit changes was the large-scale distribution
of yard signs. Peer cities also raised awareness by
collaborating with neighborhood groups, interested
residents, and local organizations and programs including
Safe Routes to School.
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School Zones and Posted Signage
None of the peer cities interview have further reduced
school zone speed limits to 15 mph after implementing
speed limit reductions to 20 mph on local streets, largely
because of the state government’s level of control
over speed limit setting in Oregon, Washington, and
Massachusetts. The City of Seattle removed the majority
of old advisory speed signs that conflicted with newly
posted 20 and 25 mph signs. Multiple municipalities noted
that speed limit reductions revealed the need for a higher
frequency of posted signage, especially on local streets
adjacent to higher-traffic streets, and the need to improve
consistency in the placement of speed limit signs.
Evaluation Process
The City of Portland and the City of Seattle are the only
interviewed cities that completed before and after data
analysis of vehicle speeds. Of note, both cities’ studies
had constraints like Boulder’s evaluation in that there was
relatively limited before/after data on which conclusions
could be drawn. In addition, it does not appear that these
cities accounted for the error (typically ± 1 mph) of their
traffic counters when presenting results.
Portland evaluated speeds before and after the reduction
of the local street speed limit from 25 mph to 20 mph in
58 locations and found:
•No change in median speed or 85th percentile speed
•Very small reductions in the percent of drivers
traveling greater than 25 (-0.5%), 30 (-1.7%), and 35
(-0.5%) mph
Seattle evaluated speeds before and after spot reductions
of the speed limit on arterials in North Seattle from 30
mph to 25 mph and found:
•Reductions in crashes (-22% for total crashes, -18%
for injury crashes)
•Reductions in 50th percentile (-9.9%), 85th percentile
speeds (-7.1%), and the percent of drivers traveling
40 mph or greater (-54.1%)
4 NACTO, Cairns et al. City Limits: Setting Safe Speed Limits on Urban Streets, 2020, p. 18
Updated Methods and Design Programs for Setting and
Reinforcing Lower Speed Limits
While design standards and methods for setting speed
limits were not significantly affected, cities found that
implementing lower speed limits revealed a need to
retrofit streets with traffic calming to reinforce the
lower speed limits. Peer cities noted that the speed limit
reductions led to a procedural shift where staff now
design streets for target speeds rather than the 85th
percentile speed, which studies have shown can lead to
increases in vehicle speeds over time.4 The speed limit
reductions also led staff to revise speed management
programs to be more context sensitive and increased the
number of streets eligible for traffic calming projects.
Enforcement
The four cities use a combination of automated
enforcement (fixed cameras and photo radar vans),
speed feedback trailers, and fixed speed radar signs
to encourage or enforce the speed limit. Many cities
expressed that enforcement is typically a short-term
solution when areas pop up as speeding hotspots either
through resident complaints, staff speed studies and/
or staff crash analysis. Cities favored an engineering
approach that redesigns streets to bring speeds down
permanently through traffic calming infrastructure
changes rather than using enforcement on an ongoing
basis.
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Recommendations
Below are recommendations for introducing or modifying speed management programs,
policies, procedures, and projects in the City of Boulder to align with “20 is Plenty.”
Topic Number
4E
Approach
Correlation
Recommendation Justification
Neighborhood
Speed
Management
Program
1
Update NSMP engineering
toolkit to include the removal of
striped centerline markings and
treatments that provide a mix of
horizontal and vertical deflection;
review guidelines and industry
best practices for speed hump
placement along streets with 20
mph speed limits.
Streets with narrower curb to curb
widths, narrower vehicle travel
lanes, and no striped centerline
are more likely to have lower
speeds. Currently, the NSMP toolkit
of engineering solutions does not
include striped centerline removal
or parklets as means to narrow
street widths. While speed humps
are included as a tool, speed hump
frequency is not defined. The
evaluation of “20 is Plenty” did not
include locations with speed humps,
but speed humps have been proven
to lower maximum speeds if spaced
appropriately.
2
Launch data-driven speed
management program
focused solely on arterial
streets, involving community
engagement instead of accepting
resident applications.
NSMP criteria allows for only local
or collector streets to be submitted
and considered for improvements,
but 65% of severe crashes occur
on arterial roads, 11% occur on
collectors, and 11% occur on local
streets in Boulder.
3
Prioritize segments of local
streets that adjoin arterial
streets.
Alongside recommendation
2, Boulder would benefit from
prioritizing traffic calming at arterial
and residential street junctions
and residential gateways adjoining
arterial streets.
Key:
Engineering Evaluation Enforcement Education
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Topic Number
4E
Approach
Correlation
Recommendation Justification
Designing for
Target Speeds
4
Revise the Design and
Construction Standards to use a
20 mph target speed for local
street design.
The City of Boulder’s current
engineering approach to designing
streets includes looking at the
speeds that 85% of motorists are
driving (85th percentile speeds) and
designing to accommodate these
speeds. In contrast, cities using
the safe system approach decide
what speed is safest to travel on a
given street and design the street
so the majority of people will drive
that target speed. Adjusting design
standards to match target speeds
(50th percentile speeds) has proven
to be successful.
5
Conduct a systematic evaluation
of existing local street widths
(and speed-related crashes) to
identify segments of concern;
prioritize segments of concern
for inclusion in future traffic
calming projects or programs
such as the NSMP.
The standard cross-section for
a residential street is a two-way
street with 30 feet of space curb
face to curb face with on-street
parking permitted. With two on-
street parking lanes of 8 feet each
this equates to 14 feet of travelled
way between parked cars. This
standard is best practice for keeping
speeds low, but some residential
streets in Boulder exceed these
widths.
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Topic Number
4E
Approach
Correlation
Recommendation Justification
Functional
Street
Classifications
6
Identify street segments
currently classified as local
streets that function as higher
classification roads.
Some streets currently classified as
Local may be a better classified as a
Collector or as somewhere between
a Local and Collector as outlined in
the next recommendation.
7
Consider reclassifying select
streets/street segments from
local to collector where the
access density, transit stop
density, emergency response
route, snowplow route, and other
characteristics relate more
closely to other streets with
higher classifications.
There are some streets currently
classified as Local streets that
serve a higher volume of traffic,
connect directly to more community
destinations, and in many cases
are wider and have a striped
centerline. Oftentimes there is a
school on these local streets. For
these streets, it may be better to
use a new street classification if the
street is a key connection for area
residents rather than a primarily
residential street.
8
Consider developing an Industrial
Street and Business Park Street
classification to better match
streets providing access to
industrial and business land
uses.
Some streets currently classified
as Local streets do not have any
adjacent residences and serve light
industrial or business uses. Because
of this context they are designed
more for large truck access.
Rather than redesigning them with
treatments more appropriate for
residential streets, a reclassification
may be a better approach –
matching their classification to the
existing design.
9
Evaluate speed limit reductions
along high-crash, high-speed
arterial corridors using the
speed limit setting framework
that will be developed in the
upcoming Community Mobility
Planning and Implementation
(CMPI) Speed Limit Setting and
Signing Framework grant project.
Arterial streets comprise 17% street
centerline miles in Boulder but
account for 65% of severe crashes.
Focusing speed reduction efforts
on key arterial street segments will
have a greater effect than focusing
only on local and collector streets.
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Topic Number
4E
Approach
Correlation
Recommendation Justification
Additional
Speed Limit
Reductions to
Support Vision
Zero
10
Prioritize arterial speed limit
reductions on high-stress
arterial corridors that also
adjoin local streets where 20
mph speed limits have been
introduced.
Some arterial streets may be
better candidates for speed limit
reductions if they are adjacent to
primarily residential land uses
where the speed limits have already
been reduced.
Speed Limit
Setting in
School Zones
11
Consider reducing speed limits
in select school zones from
20 mph to 15 mph based the
school circulation patterns, sight
distance, roadway width, nearby
land uses and other various
criteria.
The potential for a severe crash
outcome for someone walking
or bicycling is lower at 20 mph
than at 30 or 40 mph, however,
the risk is higher for children
than adults. Therefore, in some
school zone locations (especially
near elementary schools) a 15
mph speed limit may be more
appropriate to reduce the risk to
children walking and bicycling.
12
Working with partners at the
Boulder Valley School District,
identify potential locations where
School Streets (shared streets
in front of schools) could be
implemented to best support
speed reductions and encourage
mode shift.
School Streets can help encourage
walking and bicycling to school
and reduce the complexity of
interactions and potential conflicts
between students and caregivers
walking, bicycling, or driving in the
street immediately adjacent to the
school.
Standardizing
Signage 13
Through the CMPI Speed Limit
Setting and Signing Framework
grant, develop a consistent
practice for installing 20 mph
speed limit signs on local streets
and at additional key gateway
locations throughout the city.
There was a slight correlation
between streets with posted speed
limit signs and speed reductions.
Adding more speed limit signs
systematically in key locations may
assist in system-wide local street
travel speed reductions.
Warning Signs/
Advisory
Speeds
14 No Change Needed N/A
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Topic Number
4E
Approach
Correlation
Recommendation Justification
Photo Radar Van
Program and
Radar Speed
Signs
15
Periodically re-evaluate the
location of street segments on
which to deploy the photo radar
vans.
These locations are where average
vehicle speeds were the highest
and 95th percentile vehicle speeds
(excessive speeding) increased the
most in the evaluation. They may
be good candidates for targeted
enforcement as a short-term
solution while street redesigns or
other speed reduction measures are
considered.
16
Consider lobbying members
of the Colorado General
Assembly to allow automated
enforcement on arterial streets.
Vehicle speeds are higher on
arterial streets than on local streets,
however, Colorado Revised Statutes
currently only allow automated
enforcement on streets in school
zones, residential neighborhoods,
within a maintenance, construction,
or repair zone, and along streets
that border a municipal park. While
some of these conditions overlap
arterial streets, many do not.
Allowing automated enforcement on
more arterial streets can assist the
city in reducing speeds citywide in
the short-term.
17
Expand the use of both
permanent and portable radar
speed feedback signs along
arterial streets.
NSMP projects focus on local and
collector streets. Radar speed signs
could also be effective in reducing
speeds on arterial streets.
Pedestrian
Crossing
Treatment
Installation
Guidelines
18 No change needed N/A
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Topic Number
4E
Approach
Correlation
Recommendation Justification
Promotion and
Engagement
19
Increase the presence of “20 is
Plenty” yard signs and update
messaging to incorporate
statistics on speeding crashes,
speed enforcement, and
community disapproval of
speeding.
Through ongoing review of data
and coordination with the police
department, target the expansion
of photo radar van deployment to
areas with highest speeds.
20
Reintroduce other “20 is Plenty”
advertising including media
and online efforts to spread
awareness of Vision Zero.
Better understanding of the
new speed limit and reasons for
reducing it could help more people
driving comply with the speed limit.
21
Develop a Culture Change Model
approach that changes social
perceptions of the risks of
speeding.
Many communities conduct
educational campaigns that
humanize the victims of traffic
crashes which helps communicate
the negative consequences that can
occur because of speeding.
22
Communicate and collaborate
with local organizations and
existing programs like Safe
Routes to School to create and
promote campaigns specifically
focused on drivers who speed
A multi-pronged communications
approach describing different
reasons why “20 is Plenty” is
important will appeal to a broader
audience.
23 Extend speeding education to
reach beyond NSMP project sites.
The NSMP has great existing
promotional materials that could be
expanded for use on other projects
outside of NSMP streets.
Next Steps
Despite the results of the evaluation, local streets generally continue to not exhibit speed-related crash patterns, as
indicated in the Draft Safe Streets Report, 4th Edition 2022. Thus, the recommendations presented will need to be
balanced against priorities and implemented over time as part of a comprehensive Vision Zero strategy.
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