09.09.24 TAB Agenda 7.a.i Signal PracticesSignal Timing Practices Update
Transportation Advisory Board
September 9, 2024
Transportation & Mobility
|
Agenda
Transportation & Mobility Signal Timing Practices
•Signal Practices Overview
•Vision Zero Context
•Implementation Success
•Existing Signal System Context
•Scope of Work Considerations
•Next Steps
Signal Practices Overview
Signal Timing
Practices
Maintenance
Construction
Planning &
Warrants
Design
Operations
VZAP Focus
Leading
Pedestrian
Intervals
Signal Practices Overview
Transit Signal
PrioritySignal Modes &
Coordination
Operations
Exclusive
Pedestrian
Phases
Left-Turn
Phasing
Special
Event Timing
Standard
Timing Settings
Emergency
Operations
Right-Turn
on Red
Signal Practices Overview
•Left-Turn Phasing
o Permitted Only
o Protected Only
o Protected-Permitted
•Evaluation Criteria
o Physical/Geometric
o Volume
o Speed
o Crashes
o Delay
o Current left turn phasing
Signal Practices Overview
•Right-Turn on Red
•Evaluation Criteria
o Sight distance
o Multimodal volumes
o Signal phasing
o Crash history
o Intersection geometry
Signal Practices Overview
•Leading Pedestrian Intervals
•Evaluation Criteria
o Responsive
o Crash history
o Proactive
o Exposure/risk
o Opportunistic
o Impact to operations
Responsive
Is correctable
crash frequency ≥3
total in the past 3
years?
Proactive Opportunistic
Min. Ped Vol ≥ 50/hr
AND
Min. Right Turn Vol ≥ 100/hr
AND
Min. Prob 1st Veh. Is a Right-
Turn ≥ 50%
Can a min. 3 sec
LPI be
accommodated w/
minimal impact to
signal operations?
Vision Zero Context
•For the period from
2020-2023, there have
been an average of 48
severe crashes per year.
•37% of severe crashes
occur at signalized
intersections.
37%
63%
Location of Severe Crashes
Traffic Signal Other
Vision Zero Context
8.3
5
1.5
0.8
0.8
0.5 0.5 0.3 0.3
Type & Number of Severe Crashes Per Year at Signals
Approach Turn Red-Light Running Crossing Against the Signal
Reckless Driving/Speeding Rear-End Right-Turn Bypass
Right Turn on Red Right-Turn Hook Sideswipe
•Nine main crash types
have led to severe
crashes at signals.
•Approach turn and
red-light running are
the types that result in
most severe crashes.
Vision Zero Context
•Left turn related crashes
at signals currently make
up about 17% of all
annual severe crashes.
20%
17%
63%
Location of Severe Crashes
Traffic Signal Left Turn at Signal Other
Implementation Success
•Before/after analysis of
left turn phasing changes
shows a 68% reduction
in approach turn crashes.
0
20
40
60
80
100
120
140
160
Flashing Yellow
Arrow
Left Turn
Phasing
Change
LPI RTOR
Restriction
Number of Changes Installed Since 2018
Existing Signal System Context
Type of Left Turn Phasing # of Approaches % of Approaches
Permitted Only 164 33%
Shared Lane – No Left Turn Phase 76 15%
Protected-Permitted – FYA -TOD 73 15%
Protected Only – TOD 48 10%
Permitted Only – FYA 43 9%
No Conflicting Pedestrian Phase 41 8%
Protected Only – 24/7 35 7%
Protected-Permitted – TOD 9 2%
Protected-Permitted – 24/7 2 0%
Ped Protect – TOD 2 0%
Ped Protect – 24/7 1 0%
Total 494 100%
Existing Signal System Context
Permitted Only Left Turn Phasing
•Canyon Blvd/15th St – EBLT
Existing Signal System Context
Permitted Only Left Turn Phasing w/ Flashing Yellow Arrow
•Arapahoe Ave/Cherryvale Rd – WBLT
Existing Signal System Context
Pedestrian Protected Left
Turn Phasing
•30th St/Walnut St – EBLT
Existing Signal System Context
No Conflicting Pedestrian Phase
•Colorado Ave/Foothills Pkwy – EBLT
Existing Signal System Context
Shared Lane – No Left Turn Lane
•30th St/Glenwood Dr – NBLT
Scope Considerations
•New practices
•Evaluation criteria
•Tradeoffs
•Technology
•Geometric or other changes
•Prioritization methodology
Scope Considerations
•Deliverables
Takeaways
•Good crash data is essential to understanding underlying
causes
•Engineering solutions can make the system more foolproof
and forgiving
•Many solutions can be lower cost (striping or signal phasing)
•Many solutions can be win/win (improved safety with limited
operational impacts)
•Continued strategic and targeted focus on left turn crashes
can have a significant positive effect on achieving Vision Zero
Next Steps
•City Council – Matters from City Manager – October 17
•Consultant selection process – Q4 2024
•Finalize scope of work, schedule, budget – Q4 2024
•Begin work – Q1 2025
•Additional TAB/Council check-ins – Q2 2025
•Anticipated completion of practices update – Q3 2025
•Begin implementation of programming changes across High
Risk Network – Q4 2025