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City of Somerville Davis Square Signal Timing Changes May 2018 City - PowerPoint PPT Presentation

City of Somerville Davis 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


  1. City of Somerville Davis Square Signal Timing Changes May 2018

  2. 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 26s 34s 5s 14s 25s =130s cycle

  3. City of Somerville – Davis Square Signal Timing Planning Discussion May 2018 Current phasing ‐ Overview Blue arrows represent • vehicle flows (who has the green light)

  4. City of Somerville – Davis Square Signal Timing Planning Discussion May 2018 Current phasing ‐ Overview Blue arrows represent • vehicle flows (who has the green light) Green circles represent • common, but illegal pedestrian crossings during each phase

  5. City of Somerville – Davis Square Signal Timing Planning Discussion May 2018 Current phasing ‐ Overview Current phasing 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)

  6. City of Somerville – Davis Square Signal Timing Planning Discussion May 2018 Current phasing ‐ Overview Current phasing 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

  7. City of Somerville – Davis Square Signal Timing Planning Discussion April 2018 Current phasing

  8. City of Somerville – Davis Square Signal Timing Planning Discussion May 2018 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

  9. City of Somerville – Davis Square Signal Timing Planning Discussion May 2018 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

  10. City of Somerville – Davis Square Signal Timing Planning Discussion May 2018 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

  11. City of Somerville – Davis Square Signal Timing Planning Discussion May 2018 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

  12. City of Somerville – Davis Square Signal Timing Planning Discussion May 2018 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

  13. City of Somerville – Davis Square Signal Timing Planning Discussion May 2018 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)

  14. City of Somerville – Davis Square Signal Timing Planning Discussion May 2018 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

  15. City of Somerville – Davis Square Signal Timing Planning Discussion May 2018 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 –

  16. City of Somerville – Davis Square Signal Timing Planning Discussion May 2018 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

  17. City of Somerville – Davis Square Signal Timing Planning Discussion May 2018 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 + 7s LPI + 24s 5s 14s 25s 18s =100s cycle

  18. City of Somerville – Davis Square Signal Timing Planning Discussion May 2018 Current phasing – Highland Ave LPI 7 Seconds •

  19. City of Somerville – Davis Square Signal Timing Planning Discussion May 2018 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

  20. City of Somerville – Davis Square Signal Timing Planning Discussion May 2018 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

  21. City of Somerville – Davis Square Signal Timing Planning Discussion May 2018 Current phasing – College Ave LPI 7 seconds •

  22. City of Somerville – Davis Square Signal Timing Planning Discussion April 2018 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

  23. City of Somerville – Davis Square Signal Timing Planning Discussion May 2018 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

  24. City of Somerville – Davis Square Signal Timing Planning Discussion May 2018 Current phasing – MBTA Busway Phase 14 Seconds • Only conflicts are with • buses, which are relatively few and slow ‐ moving

  25. City of Somerville – Davis Square Signal Timing Planning Discussion May 2018 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 •

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