City of Bellevue s Adaptive Left Turn Phasing Presented by : Mark Poch, PE, PTOE City of Bellevue, WA May 1, 2015
130,000 pop. 197 signals
The Challenge Protected Only Turns
The Challenge Protected Only Turns Set up to run 24/7/365 No Permissive turns during light hours with gaps
The Challenge Protected/Permissive
The Challenge Protected/Permissive Conflicts with Pedestrians No Protected ONLY turns during heavy hrs
The Challenge How to provide the right LT phasing at the right time?
The Response Develop new tools SCATS Traffic Adaptive Signal System Utilize Flashing Yellow Arrow (FYA) display Pro Only vs. Pro/Per by Time of Day (TOD)
Flashing Yellow Arrow (FYA)
Protected Left Turn From 24/7/365 to TOD Systematically evaluate all Protected left turn locations citywide
Protected Left Turn From 24/7/365 to TOD 175 of 197 signalized intersections evaluated 88 protected only left turns converted to pro/per with FYA by TOD
Good strategy Protected Left Turn To Pro/Per by TOD Has shortcomings Can t respond to real time traffic and/or pedestrian conditions
Next Step From TOD to Adaptive Left Turn Control Strategy
Adaptive LT Control Strategy To replace TOD scheduling of protected vs. protected/permissive LT with a better methodology Will look at five strategies in this presentation
Adaptive LT Control Strategy 1. Opposing traffic conditions How? SCATS simple logic to disable/enable FYA Cycle length threshold Congestion level of opposing traffic SCATS - Degree of Saturation (DS) Ratio of the effective green time to the total available green time on the approach/lane Check DS of opposing thru traffic
Adaptive LT Control Strategy 1. Opposing traffic conditions 2. Resolve Pedestrian conflict with permissive portion of pro/per
Adaptive LT Control Strategy Resolve pedestrian vs. left conflict A recent controversial study by Oregon State University examined driver behavior in permissive left turns has identified about 4-9 % of the time, drivers don't even bother to look and see if there are people in the way.
Adaptive LT Control Strategy Resolve pedestrian vs. left conflict A recent controversial study by Oregon State University examined driver behavior in permissive left turns has identified about 4-9 % of the time, drivers don't even bother to look and see if there are people in the way.
Adaptive LT Control Strategy Resolve pedestrian vs. left conflict How? SCATS Ped Minus Left Feature Omit permissive portion of pro/per when the crosswalk has a walk or flashing don t walk indication.
Adaptive LT Control Strategy Resolve pedestrian vs. left conflict How? SCATS Ped Minus Left Feature Example
SCATS Ped Minus Left Feature No Ped - In FYA (Don t Walk)
Adaptive LT Control Strategy Ped Waiting Red (Don t Walk)
SCATS Ped Minus Left Feature Ped Crossing Red (Walk and FDW)
SCATS Ped Minus Left Feature After FDW FYA (Don t Walk)
Adaptive LT Control Strategy 1. Opposing traffic conditions 2. Resolve pedestrian vs. left conflict 3. Reduce accident caused by poor sight distance
Adaptive LT Control Strategy 1. Opposing traffic conditions 2. Resolve pedestrian vs. left conflict 3. Reduce accident caused by poor sight distance Blocking Queue
Adaptive LT Control Strategy 1. Opposing traffic volume 2. Resolve pedestrian vs. left conflict 3. Reduce accident caused by poor sight distance How? SCATS special logic to disable/enable FYA Measuring the congestion level of the inside lane
SCATS special logic to disable/enable FYA Example Opposing far side lane DS > 43 DS Detector
SBLT at Coal Creek Parkway/124 th Ave SE May 15, 2013 4-7 PM DS > 43 DS < 43
SBLT at Coal Creek Parkway/124 th Ave SE Disable FYA At 16:37 DS > 43 Disable FYA At 16:37
SBLT at Coal Creek Parkway/124 th Ave SE Disable FYA At 16:37 DS > 43 Protected Left Turn Disable FYA At 16:37 Protected Left Turn
SBLT at Coal Creek Parkway/124 th Ave SE Disable FYA At 16:37 DS > 43 Enable FYA At 18:09 Protected Left Turn Disable FYA At 16:37 Protected Left Turn Enable FYA At 18:09
Adaptive LT Control Strategy 1. Opposing traffic conditions 2. Resolve pedestrian vs. left conflict 3. Reduce accident caused by poor sight distance 4. Manage freeway ramp left turn traffic
Adaptive LT Control Strategy 1. Opposing traffic conditions 2. Resolve pedestrian vs. left conflict 3. Reduce accident caused by poor sight distance 4. Manage freeway ramp left turn traffic 5. Manage lagging LT phase for progression Checking DS of concurrent thru phase
Time of Day Adaptive Memorial Day Week Example
Memorial Day Memorial Day Coal Creek and 124th PM EBLT TOD PM Fri Mo Tue We Thu Fri 3:30 3:30 3:35 3:40 3:35 3:40 3:45 3:45 3:50 3:55 3:50 3:55 4:00 4:00 4:05 4:10 4:05 4:10 4:15 4:15 4:20 4:20 4:25 4:25 4:30 4:30 4:35 4:35 4:40 4:40 4:45 4:45 4:50 4:50 4:55 4:55 5:00 5:00 5:05 5:05 5:10 5:10 5:15 5:15 5:20 5:20 5:25 5:25 5:30 5:30 5:35 5:35 5:40 5:40 5:45 5:45 5:50 5:50 5:55 5:55 6:00 6:00 6:05 6:05 6:10 6:10 6:15 6:15 6:20 6:25 6:20 6:25 6:30 6:30 6:35 6:35 6:40 6:40 6:45 6:50 6:45 6:50 6:55 7:00 6:55 7:00 PM Fri Mo Tue We Thu Fri FYALT Enabled FYALT Disabled (Protected Left turn only)
Memorial Day Memorial Day Coal Creek and 124th PM EBLT TOD PM Fri Mo Tue We Thu Fri VS. 3:30 3:30 3:35 3:40 3:35 3:40 3:45 3:45 3:50 3:55 3:50 3:55 4:00 4:00 4:05 4:10 4:05 4:10 4:15 4:15 4:20 4:20 4:25 4:25 4:30 4:30 4:35 4:35 4:40 4:40 4:45 4:45 4:50 4:50 4:55 4:55 5:00 5:00 5:05 5:05 5:10 5:10 5:15 5:15 5:20 5:20 5:25 5:25 5:30 5:30 5:35 5:35 5:40 5:40 5:45 5:45 5:50 5:50 5:55 5:55 6:00 6:00 6:05 6:05 6:10 6:10 6:15 6:15 6:20 6:25 6:20 6:25 6:30 6:30 6:35 6:35 6:40 6:40 6:45 6:50 6:45 6:50 6:55 7:00 6:55 7:00 Adaptive PM Fri Mo Tue We Thu Fri FYALT Enabled FYALT Disabled (Protected Left turn only)
From Protected Only to Pro/Per Cost Savings from Reduced Delay Simulation models Value of time = $15/hr
Cost Savings per year From Protected 24/7 to TOD/Adaptive Cost Savings from Reduced Delay Simulation models Value of time = $15/hr $3,000,000 Public Cost Savings ($) Reduced Left-turn Delay Adjusted for accidents $2,700,000 Estimated $3,000,000 Estimated $2,200,000 $2,000,000 $1,300,000 $1,000,000 $600,000 $0 Phase 1 Thru Phase 2 Thru Phase 3 Thru Phase 4 Thru Phase 5
Adaptive Left turn phasing Benefits
Adaptive Left turn phasing Benefits Can respond to real time traffic congestion
Adaptive Left turn phasing Benefits Can respond to real time traffic congestion Can handle pedestrian/bike conflicts
Adaptive Left turn phasing Benefits Can respond to real time traffic congestion Can handle pedestrian/bike conflicts Can protect LT with limited sight distance
Adaptive Left turn phasing Benefits Can respond to real time traffic congestion Can handle pedestrian/bike conflicts Can protect LT with limited sight distance Can improve freeway ramp metering traffic
Adaptive Left turn phasing Benefits Can respond to real time traffic congestion Can handle pedestrian/bike conflicts Can protect LT with limited sight distance Can improve freeway ramp metering traffic Can provide better coordination as needed
Adaptive Left turn phasing Benefits Can respond to real time traffic congestion Can handle pedestrian/bike conflicts Can protect LT with limited sight distance Can improve freeway ramp metering traffic Can provide better coordination as needed Can lessen drivers frustrations
Adaptive Left turn phasing Benefits Can respond to real time traffic congestion Can handle pedestrian/bike conflicts Can protect LT with limited sight distance Can improve freeway ramp metering traffic Can provide better coordination as needed Can lessen drivers frustrations Can deliver compelling value to public
Final Thoughts WHY?? BELLEVUE INTELLIGENT TRANSPORTATION SYSTEM Net Left Turn Improvement Benefit = $3 million/yr Net SCATS traffic adaptive Benefit = $6-$9 million/yr SCATS Project Cost = $5.5 million (one time) Systematic/Signal Improvements have HIGH VALUE compared to Road Widening
Bellevue s Adaptive Left Turn Phasing Presented by Mark Poch