Davis Square Signal Timing Presentation - City of Somerville · City of Somerville –Davis Square...
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City of Somerville Davis Square Signal Timing Changes May 2018
Transcript of Davis Square Signal Timing Presentation - City of Somerville · City of Somerville –Davis Square...
City of SomervilleDavis Square Signal Timing Changes
May 2018
City of Somerville – Davis Square Signal Timing Planning Discussion May 2018
Current timing• 130‐second signal cycle in AM/PM peak
– Longer than 90‐second “ideal maximum” (NACTO) and 120‐second “target maximum” (HCM)– Long cycle lengths lead to delay for all users– May create safety issues as users more likely to run red lights in congested conditions (V/C >0.65)
• 155‐second cycle on Saturday– More delay for buses and pedestrians
• Same signal timing in AM and PM – Not adaptive to fluctuations in traffic over the course of a day– Highland Ave thru traffic experiences an average of 168s of delay in AM peak, 44s in PM peak
• Pedestrian phasing– Exclusive pedestrian phases show lower compliance than concurrent phases– Longer pedestrian delays = lower compliance
26s =130s cycle26s 34s 5s 14s 25s
City of Somerville – Davis Square Signal Timing Planning Discussion
Current phasing ‐ Overview• Blue arrows represent
vehicle flows (who has the green light)
May 2018
City of Somerville – Davis Square Signal Timing Planning Discussion
Current phasing ‐ Overview• Blue arrows represent
vehicle flows (who has the green light)
• Green circles represent common, but illegal pedestrian crossings during each phase
May 2018
City of Somerville – Davis Square Signal Timing Planning Discussion
Current phasing ‐ Overview• Blue arrows represent
vehicle flows (who has the green light)
• Green circles represent common, but illegal pedestrian crossings during each phase
• Green arrows represent legal pedestrian crossings (pedestrian signal is on)
Current phasing
May 2018
City of Somerville – Davis Square Signal Timing Planning Discussion
Current phasing ‐ Overview• Blue arrows represent
vehicle flows (who has the green light)
• Green circles represent common, but illegal pedestrian crossings during each phase
• Green arrows represent legal pedestrian crossings (pedestrian signal is on)
• Not discussed: Unsignalized crosswalks
Current phasing
May 2018
City of Somerville – Davis Square Signal Timing Planning Discussion
Current phasing
April 2018
City of Somerville – Davis Square Signal Timing Planning Discussion
Current phasing – Highland Ave phase • 26 Seconds
• Crosswalks across College used when right‐turns from Highland cease
• Crosswalk across Elm used during Day Street phase
May 2018
City of Somerville – Davis Square Signal Timing Planning Discussion
Current phasing – Holland St Phase• 26 Seconds
• Crosswalk across Day has no conflicts
• Crosswalks across College used when right‐turns from Highland stop
• Crosswalk across Dover used when there’s a gap in traffic
• Leapfrogging to divider island is common
May 2018
City of Somerville – Davis Square Signal Timing Planning Discussion
Current phasing – College Ave phase• 34 Seconds
• Crosswalk across Holland used during this phase, as College right‐turn volume is low (28 AM, 35 PM, 27 Saturday)
• Crosswalk across Day has no conflicts
• Peds cross Highland if no cars are in the right‐turn lane
• Leapfrogging to divider island is common
May 2018
City of Somerville – Davis Square Signal Timing Planning Discussion
Current phasing – College Clearance• 5 seconds
• Phase used to clear out area in front of busway
• No conflicts to cross Highland
• No conflicts to cross College at MBTA station
May 2018
City of Somerville – Davis Square Signal Timing Planning Discussion
Current phasing – MBTA Busway Phase• 14 Seconds
• MBTA bus phase, but relatively few buses
– In AM, 9 left turns and 9 right turns
– In PM, 5 left turns and 8 right turns
– On Saturday midday, 6 left turns and 7 right turns
• All crosswalks appear relatively safe to use
• Crosswalks across Day, Dover, and Highland are 100% safe to use
May 2018
City of Somerville – Davis Square Signal Timing Planning Discussion
Current phasing – Pedestrian Phase• 25 Seconds
• Exclusive pedestrian phase; all pedestrian signals on, all traffic stopped
• Long enough to cross one leg of intersection, but no more (few exceptions)
May 2018
City of Somerville – Davis Square Signal Timing Planning Discussion
Current phasing ‐ Issues• 25 Seconds
• Exclusive pedestrian phase; all pedestrian signals on, all traffic stopped
• Long enough to cross one leg of intersection, but no more (few exceptions)
• Example: Takes between 3.5 and 6.5 minutes (3 walk cycles) to legally walk between JP Licks and Oath
May 2018
City of Somerville – Davis Square Signal Timing Planning Discussion
Current phasing ‐ Issues• 25 Seconds
• Exclusive pedestrian phase; all pedestrian signals on, all traffic stopped
• Long enough to cross one leg of intersection, but no more (few exceptions)
• Pedestrians “scramble” outside of crosswalks
– May result in pedestrians in the intersection after the phase ends
– Not possible for all users
May 2018
City of Somerville – Davis Square Signal Timing Planning Discussion
Bottom line• Existing phasing is:
– Encouraging potentially dangerous pedestrian movements
– Extremely time‐consuming for pedestrians
– Or both
• The “Don’t Walk” signal sends mixed messages
– Mandate or suggestion?
• Knowledge of the intersection is key if you want to navigate the Square in a timely manner
• Davis Square intersection can act as a barrier
May 2018
City of Somerville – Davis Square Signal Timing Planning Discussion
Proposed phasing• 100‐second signal cycle
– 30‐55 seconds shorter than existing– Reduced delay for all users
• Concurrent and “protected” pedestrian phases– Pedestrians legally allowed to cross during parallel vehicle traffic– Where there are turning conflicts, pedestrians given 7‐second “head start” (Leading Pedestrian
Interval)– Peds always allowed to cross when there is no conflict present
• Exclusive pedestrian phase removed– Reduces cycle length
7s LPI +25s =100s cycle24s
7s LPI +18s 5s 14s
May 2018
City of Somerville – Davis Square Signal Timing Planning Discussion
Current phasing – Highland Ave LPI• 7 Seconds
May 2018
City of Somerville – Davis Square Signal Timing Planning Discussion
Current phasing – Highland Ave phase • 25 Seconds
• Right‐turning vehicles from Highland Avenue must yield to pedestrians
• Day Street vehicles must yield to peds crossing Elm
May 2018
City of Somerville – Davis Square Signal Timing Planning Discussion
Current phasing – Holland St Phase• 24 Seconds
• Crosswalk across Day Street has no conflicts
• Highland Avenue right‐turners must yield to peds
• Highland Avenue left‐turners and Holland Street right‐turners must yield to peds
May 2018
City of Somerville – Davis Square Signal Timing Planning Discussion
Current phasing – College Ave LPI• 7 seconds
May 2018
City of Somerville – Davis Square Signal Timing Planning Discussion
Current phasing – College Ave phase• 18 seconds
• Small number of right‐turns must yield to peds crossing Holland Street
• No conflicts for peds crossing Day Street
April 2018
City of Somerville – Davis Square Signal Timing Planning Discussion
Current phasing – College Clearance• 5 seconds
• Phase used to clear out area in front of busway
• No conflicts to cross Highland Avenue
• No conflicts to cross College at MBTA station
May 2018
City of Somerville – Davis Square Signal Timing Planning Discussion
Current phasing – MBTA Busway Phase• 14 Seconds
• Only conflicts are with buses, which are relatively few and slow‐moving
May 2018
City of Somerville – Davis Square Signal Timing Planning Discussion
Benefits• Reduced cycle length = less delay for all users
• Improved vehicle operations– Average improvement of 35 seconds in AM peak– Average improvement of 8 seconds in PM peak– MBTA busway delay reduced by 15 seconds
• Pedestrian delay significantly reduced– Existing maximum delay was 105 for all crossings – Future pedestrian delay improves by 24 and 99 seconds depending on crosswalk location/time of day
Over the course of an hour:• Each crosswalk would get a “Walk” signal 8 more times• Highland Avenue would get about 3 more minutes of green time• Holland Street would get about 2.5 more minutes of green time• MBTA busway would get 8 more green signals
May 2018
