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” (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 cycle 26s 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”
• utside 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 cycle 24s 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