20260727 - TSP Plans - Union Sq Somerville.pdf
PDF 3 MB Posted
- Attached to
- IFB 115-26 Transit Signal Priority Project
- Solicitation number
- BD-27-1206-40000-40000-132413
- Issued by
- Middlesex County, Massachusetts
About this file
This is a Transit Signal Priority (TSP) Plans document prepared by the Massachusetts Bay Transportation Authority (MBTA) for the Union Square corridor in Somerville, Massachusetts, dated August 5, 2026. The project implements TSP technology at three signalized intersections—Washington Street & Somerville Avenue & Webster Avenue, Somerville Avenue & Prospect Street, and Prospect Street & Webster Avenue—to improve transit operations for five bus routes (Routes 85, 87, 91, 109, and CT2) and trolley service. The TSP system modifies signal timing in real-time to provide green extensions or early green phases for transit vehicles, thereby reducing wait times and improving service reliability. The document provides detailed technical specifications for signal timing, phasing sequences, and TSP channel configurations for each intersection, with separate signal timing plans for morning peak (6 AM–10 AM), evening peak (3 PM–7 PM), and free-operation periods. TSP implementation uses two primary strategies: green extension, which extends a phase when a transit vehicle is expected to arrive at the end of the signal phase, and early green, which shortens preceding phases to allow an earlier start for the transit phase. All TSP operations maintain compliance with minimum green times, pedestrian walk and clearance intervals, and yellow and red clearance phases.
The TSP system operates through a Priority Request Generator (PRG) that continuously generates messages based on geofence placement, transit stop locations, vehicle speed, and service status. Each TSP channel corresponds to a specific transit movement and priority level, with reservice lockout times of 120 seconds during coordinated operations (Plans 1 and 2) and no lockout during free operation. Maximum extension and reduction values are precisely calculated for each phase and intersection to prevent excessive disruption to other road users while optimizing transit performance. The document was designed by Martin Bertini and Diederick VanDillen of Jacobs Engineering and requires approval signatures from the MBTA representative and municipality/owner representative. Peak service frequencies range from 10 to 30 minutes depending on the route, and TSP priority is permitted at all times across all channels. The signal timing plans maintain 120-second cycle lengths during peak coordinated operations with specific offsets and phase splits detailed for each intersection to ensure network coordination while accommodating transit priority requests.
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TSP PLANS
UNION SQUARE, SOMERVILLE, MA
Date:
MBTA POINT OF CONTACT
Jay Jackson, PE
TSP Sr Technical Manager jayjackson@mbta.com
(617) 549-7859
TRANSIT BUS SERVICES THROUGH CORRIDOR
1 Route 85
2 Route 87
3 Route 91
4 Route 109
5 Route CT2
PROJECT INTERSECTIONS
1 Washington Street & Somerville Avenue
2 Prospect Street & Somerville Avenue
3 Prospect Street & Webster Avenue
8/5/2026
PROJECT AREA DETAIL
The Transit Signal Priority (TSP) Plan provides a detailed operational description of each signalized intersection within the project area for TSP service implementation. The document should be used together with any project signal construction plans and standard specifications to provide a complete understanding of the overall design.
20260727 - TSP Plans - Union Sq, Somerville Printed on 8/7/2026 Page 1 of 10
EXECUTIVE SUMMARY
This image is for illustrative purposes only. See detail sheet for actual timings.
TSP Overview
Transit signal priority (TSP) is being implemented in this corridor to improve transit (trolley and bus) operations. TSP makes real-time modifications to signal timing to increase the likelihood that an intersection approach will have a green indication when a transit vehicle arrives, or else to reduce the time a transit vehicle has to wait at a red light.
TSP Implementation
In this project, TSP is being added on top of existing signal timing and phasing, which will remain as currently exists. TSP will never skip a yellow or red clearance phase, skip pedestrian walking and clearance time, reduce the duration of signal phase beyond what is allowable to maintain minimum green requirements, or skip a phase entirely when there is any demand for that phase.
TSP Strategies in this project (see right )
• A green extension is triggered when a transit vehicle is expected to arrive to the intersection shortly the end of its signal phase, and miss its opportunity to cross the intersection during a given cycle. When green extension is called, the phase is extended to maintain the green indication untin the transit vehicle has crossed. Subsequent phases are shortened by some allowable amount.
• An early green is triggered when a transit vehicle is waiting at a red indication or is expected to arrive to the intersection shortly before the beginning of its signal phase and have to wait for green. When an early green is called, the phase(s) before the one required by the transit vehicle are shortened by some allowable amount, for the transit phase to begin earlier.
TSP Strategies not in this project
Other TSP strategies like phase insertion, phase reservicing, skipping phases, skipping pedestrian movements, phase order changes, and breaking coordination will not be implemented in this project.
20260727 - TSP Plans - Union Sq, Somerville Printed on 8/7/2026 Page 2 of 10
TSP TECHNICAL IMPLEMENTATION
General Notes TSP Timing Settings
For a given phase, its green time is
During free operations: Green = Maximum Green
During coordinated operations: Green = Phase Split - LPI* - Yellow Clearance - Red Clearance
* Leading Pedestrian Interval, if present
Priority Request Generator (PRG) and TSP Requests Spare green is determined as the smaller of the following two calculations
Spare Green A = Green - Minimum Green
Spare Green B = Green - Pedestrian Walk - Pedestrian Clearance
Maximum Reduction ≤ Spare Green
Maximum Extension ≤ Σ Maximum Reductions on other phases
1. Actual transit schedules may adjust with service changes. For up to date information, reference mbta.com and GTFS and GTFS/RT feed. (General Transit
Feed Specification/Real Time)
2. All signal/TSP timings shown are in seconds unless otherwise noted.
The maximum a phase can be reduced by and not infringe on its minimum green and pedestrian durations is its entire spare green. However, a smaller maximum may be used if necessary to prevent excessive impact to other road users. The maximum reduction setting is programmed into the controller, which can then shorten phases by up to this amount to serve a transit vehicle on another approach
The maximum a phase can be extended by is the sum of the maximum reductions on all other non-concurrent phases. However, a smaller maximum may be used if necessary to prevent excessive impact to other road users. The maximum extension setting is programmed into the controller, which can then lengthen a phase by up to this amount to serve a transit vehicle on that approach
PRG System
1. The PRG system determines when a transit vehicle would benefit from TSP and sends a PRG message with a TSP request to the signal controller.
2. PRG messages shall be automatically and continuously generated based on geofence zone placement, speeds, transit stop locations, and other site-specific conditions.
3. PRG messages are only generated when a transit vehicle is en-route and in service as determined by configurable PRG logic (Unconditional Service).
4. The PRG shall only have one priority service request active with the traffic signal controller at a time.
5. Priority within a class type and level is the same, typically issued on a first-come-first-served (FCFS) basis (closest vehicle based on ETA), and persistently applied without any relative priority considerations given to route or direction.
PRG messages shall include
1. TSP channel and strategy being requested based on transit route and direction.
(See intersection sheets for details about TSP channels and strategies).
2. Time of Service Desired (TSD), indicating the expected time of arrival (ETA) of the transit vehicle at the intersection stop bar based on the current time, bus position and speed.
3. Time of Expected Departure (TED), indicating the expected time of departure from the far side of the intersection (clearing the intersection) based on the current time, bus position and speed.
4. Time to Live (TTL), indicating the duration for which the request message is to remain active and valid.
These parameters shall be fine tuned based on field testing and observations.
20260727 - TSP Plans - Union Sq, Somerville Printed on 8/7/2026 Page 3 of 10
READING TSP PLANS
TSP Channel Number 1 2
Priority Movement EBT NBT
Corresponding Phase Φ2 Φ4 Existing Phasing Mainline Side street
Applies to Route(s) 109 87 Φ2: Avenue A Φ4: Main St
Peak Service Frequency 12 min 18 min No TSP
When is Priority Permitted? All Times All Times
Minimum
Green Extension ✓ ✓ Channel 1 (Avenue A EBL)
Early Green ✓ ✓ Φ2: Avenue A Φ4: Main St
Phase Insertion or Reservice ✗ ✗ Green
Skips Phases ✗ ✗ Ext Minimum
Skips Ped Movements ✗ ✗
Phase Order Changes ✗ ✗
Breaking Coordination ✗ ✗
Phase Φ2 Φ4
Minimum Green 7 12
Extension - 3
Max Green 50 53
Yellow Change 3 3
Red Clearance 2 2
Recall OFF/OFF MAX/OFF
Ped Walk 0 0
Ped Clearance 0 0
Plan Days and Time Cycle (s) Offset (s) Φ2 Φ4
1 M-F 6AM-10AM 90 67 42 48
2 M-F 3PM-7PM 90 60 35 55
Free all other times - - -
Max Reduction (s)
Reservice (s)
Max Extension (s)
Plan
TSP CHANNEL 1 (Ave A EBT)
TSP CHANNEL 2 (Main St NBT)
Plan
Max Extension (s)
Φ4=36 Φ4=41
90 90 -Reservice (s)
Max Reduction (s)
Φ4=43
FREE
1 2 FREE
Φ2=29Φ2=36 Φ2=41
Φ2=21
Φ2=28
Φ2=43
Φ4=21
Φ4=28
Φ4=29
Minimum 1 cycle1 cycle
Lockout Time between TSP
Calls
Minimum Green
Strategy:
Green Extension
PLAN DATA
Avenue A
TSP SETTINGS
Roadway Main St
SIGNAL TIMING
In this example, traffic signals are pre-timed and coordinated in the AM and PM peak periods (plan 1 and 2, respectively).
During other times, the signal is in free operation which means that it detects vehicles and responds to traffic demand by adjusting phase durations
The signal timing and plan data tables show how the signal controller is programmed and describe how signal timing works when not
TSP is requested. These tables were obtained from existing traffic signal plans and shown in this package with no modifications.
The TSP channel detail table describes the settings applied to a TSP Channel.
Each column shows the settings for each signal plan (i.e. time of day) corresponding to the plan data table.
The maximum extension for the TSP phase, shows up to how many seconds TSP can add to a phase.
The maximum reduction for all other phases, shown in seconds, is calculated to not infringe on minimum durations.
Reservice is the length of time that must pass after TSP is granted before the same channel can be called again, also called lockout
The TSP Settings table shows an overview of the
TSP configuration for an intersection.
Each column of the table represents a TSP
Channel. The channel a
TSP request is made on indicates to the controller which movement of traffic needs TSP.
Each of these rows is an available TSP strategy.
The designers and roadway owners decide whether to implement each strategy or not by weighing expected benefit to transit vehicles against potential disruptions to other road users and overall network performance.
Each vehicular phase finishes with a yellow and a red clearance interval.
These arrows represent the directions of traffic that are allowed in a given phase.
One or more later phases are shortened to allow the signal cycle to end on time, but without infringing on its minimum duration.
In this example, the first phase gets additional green time at the end to allow a bus to cross the intersection before the light changes to red.
A signal phase is a period of time in which particular traffic movements are allowed. When read left to right, these diagrams represent a traffic signal's phasing sequence.
For each intersection, the first diagram shows the existing phasing sequence, with no modifications from
TSP.
The following diagrams show each of the possible ways the phasing sequence can be modified by TSP.
The direction of traffic served by a channel.
E.g.: NBT = northbound
Each phase has a minimum duration determined by vehicular operations and/or safe pedestrian crossing time. TSP cannot reduce or infringe on a phase's minimum.
20260727 - TSP Plans - Union Sq, Somerville Printed on 8/7/2026 Page 4 of 10
1. WASHINGTON STREET & SOMERVILLE AVENUE & WEBSTER AVENUE
TSP SETTINGS Existing Phasing Leading Mainline Lagging WBL Split minor approaches
TSP Channel Number 1 2 3 4 5 LB/TI Φ2 & Φ6: EB/WB Φ1 & Φ6: WBL/T Φ4: Somerville SB Φ3: Webster NB Φ9: Pedestrian
No TSP
Priority Movement EBT WBT SBT/L,WBR NBT WBL Minimum Minimum Minimum Minimum Minimum
Corresponding Phase LB/TI, Φ2 Φ6 Φ4 Φ3 Φ1
Applies to Route(s) 109 109 85,87 85 91,CT2 TSP Channel 1 (Washington St EBT)
Peak Service Frequency 12 min 12 min 12 min 30 min 12 min LB/TI Φ2 & Φ6: EB/WB Φ1 & Φ6 Φ4: Somerville SB Φ3: Webster NB Φ9: Pedestrian
When is Priority Permitted? All Times All Times All Times All Times All Times Green Extension Min Green Minimum Green G Extension Minimum Minimum Min Minimum
Lockout Time between TSP Calls 1 cycle 1 cycle 1 cycle 1 cycle 1 cycle
Green Extension ✓ ✓ ✓ ✓ ✓ LB/TI Φ2 & Φ6: EB/WB Φ1 & Φ6: WBL/T Φ4: Somerville SB Φ3 Φ9: Pedestrian LB/TI
Early Green ✓ ✓ ✓ ✓ ✓ Early Green Min Green Minimum Green Minimum Minimum Min Minimum Early G
Phase Insertion or Reservice ✗ ✗ ✗ ✗ ✗
Skips Phases ✗ ✗ ✗ ✗ ✗ TSP Channel 2 (Somerville Ave WBT)
Skips Ped Movements ✗ ✗ ✗ ✗ ✗ LB/TI Φ2 & Φ6: EB/WB Φ1 & Φ6 Φ4: Somerville SB Φ3: Webster NB Φ9: Pedestrian
Phase Order Changes ✗ ✗ ✗ ✗ ✗ Green Extension Minimum Minimum Green G Extension Minimum Minimum Min Minimum
Breaking Coordination ✗ ✗ ✗ ✗ ✗
Φ2 & Φ6: EB/WB Φ1 & Φ6: WBL/T Φ4: Somerville SB Φ3: Webster NBΦ9: Pedestrian LB/TI
LEGEND Early Green Early G Minimum Green Min Minimum
Green time for a given phase
Additional green time, see Detail Sheet Additional Green TSP Channel 3 (Somerville Ave SBT/L,WBR)
Yellow clearance time LB/TI Φ2 & Φ6: EB/WB Φ1 & Φ6: WBL/T Φ4: Somerville SB Φ3: NB Φ9: Pedestrian
Red clearance time Green Extension Minimum Minimum Minimum G Extension Minimum
Minimum green and pedestrian walk and clearance time Minimum Minimum
LB/TI Φ2 & Φ6: EB/WB Φ1 & Φ6 Φ3 & Φ6: WBL/T Φ3: Webster NB Φ9: Pedestrian
INTERSECTION LOCATION Early Green Minimum Minimum Minimum Early G Min Green Minimum
TSP Channel 4 (Webster Ave NBT)
Φ9 LB/TI Φ2 & Φ6: EB/WB Φ1 & Φ6 Φ4: Somerville SB Φ3: Webster NB Φ9
Green Extension Minimum Minimum Minimum Minimum G Extension
LB/TI Φ2 & Φ6: EB/WB Φ1 & Φ6: WBL/TΦ4: Somerville SB Φ3: Webster NB Φ9: Pedestrian
Early Green Minimum Minimum Minimum Minimum Early G Minimum
TSP Channel 5 (Somerville Ave WBL)
LB/TI Φ2 & Φ6: EB/WB Φ1 & Φ6: WBL/T Φ4: Somerville SB Φ3: Webster NB Φ9: Pedestrian
Green Extension Minimum Minimum Min Green G Extension Minimum Min Minimum
Φ2 & Φ6: EB/WB Φ1 & Φ6: WBL/T Φ4: Somerville SB Φ3: Webster NB Φ9: Pedestrian LB/TI
Diagrams for illustrative purposes only. See detail sheet for timings. Early Green Minimum Green Early G Min Green Minimum Min Minimum
Somerville
Ave Roadway
Washington
St
Somerville
Ave
Somerville
Ave
Webster
Ave
Min
Minimum Minimum Minimum
Min Green Min
Min
Min Minimum
Min
20260727 - TSP Plans - Union Sq, Somerville Printed on 8/7/2026 Page 5 of 10
1. WASHINGTON STREET & SOMERVILLE AVENUE & WEBSTER AVENUE
PREFERENTIAL PHASING SEQUENCE SIGNAL TIMING
LB/TI Φ2&Φ6 Φ1&Φ6 Φ4 Φ3 Φ9 Plan 1 2 Free
6 25 10 7 7 - Max Extension (s) Φ2 = 13 Φ2 = 13 Φ2 = 20
- 3 2 6 3 -
6 35 13 22 19 -
6 57 16 45 45
- 3 3 3 3 - Reservice (s) 120 120 -
- 3 3 3 3 3
Plan 1 2 Free
6 4 - - 8 8 Max Extension (s) Φ6 = 13 Φ6 = 13 Φ6 = 20
20 - - - 20
PLAN DATA Reservice (s) 120 120 -
Plan Days and Time Cycle (s) Offset (s) LB/TI Φ2&Φ6 Φ1&Φ6 Φ4 Φ3 Φ9
1 M-F 6AM-10AM 120 64 6 27 16 23 17 31
2 M-F 3PM-7PM 120 53 6 27 16 23 17 31 Plan 1 2 Free
Free all other times - - - - Max Extension (s) Φ4 = 3 Φ4 = 3 Φ4 = 20
NOTES
Reservice (s) 120 120 -
Plan 1 2 Free
Max Extension (s) Φ1 = 10 Φ1= 10 Φ1 = 20
Plan Date: 8/5/2026
MBTA Representative Approval & Signature: Reservice (s) 120 120 -
Municipality/Owner Representative Approval & Signature: Plan 1 2 Free
Max Extension (s) Φ1 = 13 Φ1 = 13 Φ1 = 20
Designer Representative Information:
Designed By: Martin Bertini, Jacobs Engineering.
Edited By: Diederick VanDillen, Jacobs Engineering Reservice (s) 120 120 -
Max Green 2*
Max Green*
Extension*
Minimum Green*
MAX/
PED
MAX/
PED
Recall* PEDPEDMINOFF
Yellow Change
* Applicable during free operation only.
1. Preferential phasing sequence, signal timing, and plan data tables were obtained from signal plans and shown on this sheet without modification.
2. Values shown in blue indicate a design maximum value used, which is lower than the calculated maximum.
TSP Channel 1 (Washington St EBT)
Φ4 = 10
Φ3 = 3
Φ4 = 10
Φ3 = 3 Max Reduction (s)
Φ1&6 = 3
Φ4 = 15
Φ3 = 11
TSP Channel 3 (Somerville Ave SBT/L,WBR)
TSP Channel 4 (Webster Ave NBT)
Φ2&6 = 10
Φ1&6 = 3
Φ3 = 11
Φ3 = 3Φ3 = 3Max Reduction (s)
Phase
Ped Clearance
Ped Walk
Red Clearance
Φ2&6 = 10
Φ4 = 15
Φ3 = 11
Φ4 = 10
Φ3 = 3
Φ4 = 10
Φ3 = 3 Max Reduction (s)
TSP Channel 2 (Somerville Ave WBT)
Max Reduction (s) Φ4 = 10
Φ3 = 3
Φ4 = 10
Φ3 = 3
Φ4 = 15
Φ3 = 11
Φ2&6 = 10
Φ1&6 = 3
Φ4 = 15
Φ4 = 10Φ4 = 10Max Reduction (s)
TSP Channel 5 (Somerville Ave WBL)
20260727 - TSP Plans - Union Sq, Somerville Printed on 8/7/2026 Page 6 of 10
2. SOMERVILLE AVENUE & PROSPECT STREET
TSP SETTINGS Diagrams for illustrative purposes only. See detail sheet for timings.
TSP Channel Number 1 2 3 4
Existing Phasing Split Minor Approaches Mainline
Φ2: Somerville EB & Prospect St SBR Φ6: Somerville WB Φ4 & Φ8: Prospect St NB & SB
Priority Movement EBT/L WBT NBT SBR No TSP
Corresponding Phase Φ2 Φ6 Φ8 Φ2
Applies to Route(s) 87,109 87 91,CT2 91,109,CT2 Minimum Minimum Minimum
Peak Service Frequency 12 min 18 min 15 min 12 min
When is Priority Permitted? All Times All Times All Times All Times Channel 1 (Somerville Ave EBT/L) / Channel 4 (Prospect St SBR)
Lockout Time between TSP Calls 1 cycle 1 cycle 1 cycle 1 cycle Φ2: Somerville EB & Prospect St SBR Φ6: Somerville WB Φ4 & Φ8: Prospect St NB & SB
Green Extension ✓ ✓ ✓ ✓ Green Extension Green
Early Green ✓ ✓ ✓ ✓ Minimum Green Extension Minimum Minimum
Phase Insertion or Reservice ✗ ✗ ✗ ✗
Skips Phases ✗ ✗ ✗ ✗ Φ2: Somerville EB & Prospect St SBR Φ6: Somerville WB Φ4 & Φ8: Prospect St Φ2: EB/SB
Skips Ped Movements ✗ ✗ ✗ ✗ Early Green Early
Phase Order Changes ✗ ✗ ✗ ✗ Minimum Green Minimum Minimum Green
Breaking Coordination ✗ ✗ ✗ ✗
Channel 2 (Somerville Ave WBT)
LEGEND Φ2: Somerville EB & Prospect St SBR Φ6: Somerville WB Φ4 & Φ8: Prospect St NB
Green time for a given phase Green Extension Green
Additional green time, see Detail Sheet Additional Green Minimum Minimum Green Extension Minimum
Yellow clearance time
Red clearance time Φ2: Somerville EB & Prospect St SBR Φ6: Somerville WB Φ4 & Φ8: Prospect St NB
Minimum green and pedestrian walk and clearance time Minimum Minimum Early Green Early
Minimum Green Minimum Green Minimum
INTERSECTION LOCATION
Channel 3 (Prospect St NBT)
Φ2: Somerville EB & Prospect St SBR Φ6: Somerville WB Φ4 & Φ8: Prospect St NB
Green Extension Green
Extension Minimum Minimum Minimum Green
Φ2: Somerville EB & Prospect St SBR Φ4: Somerville SB Φ4 & Φ8: Prospect St NB
Early Green Early
Minimum Minimum Green Minimum Green
Roadway Somerville
Ave
Somerville
Ave Prospect St Prospect St
20260727 - TSP Plans - Union Sq, Somerville Printed on 8/7/2026 Page 7 of 10
2. SOMERVILLE AVENUE & PROSPECT STREET
Φ2 Φ6 Φ4 & Φ8 Plan 1 2 Free
15 20 17 Max Extension (s) Φ2 = 13 Φ2 = 17 Φ2 = 20
3 3 3
53 30 35
48 33 43
3 3 3 Reservice (s) 120 120 -
3 3 3
MAX/PED OFF OFF
5 5 4 Plan 1 2 Free
6 6 1 Max Extension (s) Φ6 = 20 Φ6 = 20 Φ6 = 20
12 17 19
PLAN DATA Reservice (s) 120 120 -
Plan Days and Time Cycle (s) Offset (s) Φ2 Φ6 Φ4 & Φ8
1 M-F 6AM-10AM 120 67 49 33 38
2 M-F 3PM-7PM 120 60 45 33 42 Plan 1 2 Free
Free all other times - - - - Max Extension (s) Φ4&8 = 20 Φ4&8 = 20 Φ4&8 = 20
NOTES
Reservice (s) 120 120 -
Plan 1 2 Free
Max Extension (s) Φ2 = 13 Φ2 = 17 Φ2 = 20
Plan Date:
MBTA Representative Approval & Signature: Reservice (s) 120 120 -
Municipality/Owner Representative Approval & Signature:
Designer Representative Information:
Designed By: Martin Bertini, Jacobs Engineering.
Edited By: Diederick VanDillen, Jacobs Engineering
Max Reduction (s) Φ6 = 10
Φ4&8 = 18
Φ6 = 2
Φ4&8 =15
Φ6 = 2
Φ4&8 = 11
Channel 4 (Prospect St SBR)
Φ4&8 = 18
Φ2 = 20 Max Reduction (s)
Φ2 = 20
Φ6 = 10
Φ2 = 19
Φ6 = 2 Max Reduction (s)
Φ2 = 20
Φ6 = 2
Max Reduction (s) Φ6 = 2
Φ4&8 = 11
Φ6 = 2
Φ4&8 =15
Φ6 = 10
Φ4&8 =18
* Applicable during free operation only.
1. Preferential phasing sequence, signal timing, and plan data tables were obtained from signal plans and shown on this sheet without modification.
2. Values shown in blue indicate a design maximum value used, which is lower than the calculated maximum.
8/5/2026
Phase
Channel 1 (Somerville Ave EBT/L)
Channel 2 (Somerville Ave WBT)
Channel 3 (Prospect St NBT)
Yellow Change
Max Green 2*
Max Green*
Extension*
Minimum Green*
Ped Clearance
Ped Walk
LPI
Recall*
Red Clearance
Φ4&8 = 11
Φ2 = 20
Φ4&8 = 15
Φ2 = 19
20260727 - TSP Plans - Union Sq, Somerville Printed on 8/7/2026 Page 8 of 10
3. PROSPECT STREET & WEBSTER AVENUE
TSP SETTINGS Diagrams for illustrative purposes only. See detail sheet for timings.
TSP Channel Number 1 2 3
Existing Phasing Minor Approaches Leading Mainline
Φ2 & Φ6: Webster Ave NB & SB LB/TI Φ4 & Φ8: Prospect St EB & WB Φ9: Pedestrian
Priority Movement NBT/R SBT/R EBT No TSP
Corresponding Phase Φ2 Φ6 Φ4,Φ8
Applies to Route(s) 85,CT2 85,91,CT2 91 Min
Peak Service Frequency 15 min 10 min 15 min
When is Priority Permitted? All Times All Times All Times Channel 1 (Webster Ave NBT/R) / Channel 2 (Webster Ave SBT/R)
Lockout Time between TSP Calls 1 cycle 1 cycle 1 cycle Φ2 & Φ6: Webster Ave NB & SB LB/TI Φ4 & Φ8: Prospect St EB & WB Φ9: Pedestrian
Green Extension ✓ ✓ ✓ Green Extension Green
Early Green ✓ ✓ ✓ Extension Minimum
Phase Insertion or Reservice ✗ ✗ ✗
Skips Phases ✗ ✗ ✗ Φ2 & Φ6: Webster Ave NB & SB LB/TI Φ4 & Φ8: Prospect St EB & WB Φ9: Pedestrian
Skips Ped Movements ✗ ✗ ✗ Early Green Early
Phase Order Changes ✗ ✗ ✗ Green
Breaking Coordination ✗ ✗ ✗
Channel 3 (Prospect St EBT)
LEGEND Φ9: Ped Φ2 & Φ6: Webster Ave NB & SBLB/TI Φ4 & Φ8: Prospect St EB & WB Φ9
Green time for a given phase Green Extension Green
Additional green time, see Detail Sheet Additional Green Minimum Min Extension Min
Yellow clearance time
Red clearance time Φ2 & Φ6: Webster Ave NB & SBLB/TI Φ4 & Φ8: Prospect St EB & WB Φ9: Pedestrian
Minimum green and pedestrian walk and clearance time Minimum Minimum Early Green Early
Green Min
INTERSECTION LOCATION
Minimum
MinMin Green
Prospect
St
Minimum
Min Green MinimumMin
MinimumMinimumMinimum
Minimum
Minimum
Minimum Green
Minimum Green
Roadway Webster
Ave
Wesbter
Ave
20260727 - TSP Plans - Union Sq, Somerville Printed on 8/7/2026 Page 9 of 10
3. PROSPECT STREET & WEBSTER AVENUE
Φ2&Φ6 LB/TI Φ4&Φ8 Φ9 Plan 1 2 Free
10 6 10 - Max Extension (s) Φ2&6 = 20 Φ2&6 = 20 Φ2&6 = 20
3 - 3 - Max Reduction (s) Φ4&8 = 20 Φ4&8 = 20 Φ4&8 = 20
43 6 56 - Reservice (s) 120 120 -
44 6 78
3 3 3 -
4 - 4 - Plan 1 2 Free
Max Extension (s) Φ2&6 = 20 Φ2&6 = 20 Φ2&6 = 20
Max Reduction (s) Φ4&8 = 20 Φ4&8 = 20 Φ4&8 = 20
0 0 0 9 Reservice (s) 120 120 -
0 0 0 19
Plan 1 2 Free
PLAN DATA Max Extension (s) 8 = 20 8 = 18 8 = 20
Plan Days and Time Cycle (s) Offset (s) Φ2&Φ6 LB/TI Φ4&Φ8 Φ9 Max Reduction (s) Φ2&6 = 20 Φ2&6 = 18 Φ2&6 = 20
1 M-F 6AM-10AM 120 0 42 9 46 23 Reservice (s) 120 120 -
2 M-F 3PM-7PM 120 0 35 9 53 23
Free all other times - - - -
NOTES
Plan Date:
MBTA Representative Approval & Signature:
Municipality/Owner Representative Approval & Signature:
Designer Representative Information:
Designed By: Martin Bertini, Jacobs Engineering.
Edited By: Diederick VanDillen, Jacobs Engineering
Max Green 2*
Max Green*
Extension*
Ped Clearance
Ped Walk
Channel 3 (Prospect St EBT)
* Applicable during free operation only.
1. Preferential phasing sequence, signal timing, and plan data tables were obtained from signal plans and shown on this sheet without modification.
2. Values shown in blue indicate a design maximum value used, which is lower than the calculated maximum.
8/5/2026
Channel 1 (Webster Ave NBT/R)
Channel 2 (Webster Ave SBT/R)
Minimum Green*
Phase
OFF/
PED
OFF/
OFF
OFF/
OFF
MAX/
OFF
Recall*
Red Clearance
Yellow Change
20260727 - TSP Plans - Union Sq, Somerville Printed on 8/7/2026 Page 10 of 10
| 20260727 - TSP Plans - Union Sq, Somerville |
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