FAQs
What is transit signal priority?
Transit signal priority, or TSP, is a set of strategies used to reduce delay and improve reliability for buses at traffic signals. One of these strategies is to implement smarter signal programming that adjusts to traffic levels, which helps all vehicle including buses. TSP equipment can also communicate with buses to give them a few extra seconds to make it through an intersection without having to stop or severely impact traffic. In some cases, TSP includes specialized traffic signals just for buses that are triggered when the bus is arriving. Examples of these signals in Somerville include Washington Street at Innerbelt Road and Holland Street in Davis Square.
What are some of the benefits of TSP?
By increasing the reliability that a bus will fulfill its designated route in the scheduled time frame, the MBTA can more accurately develop schedules, sometimes even reducing scheduled layover time and increasing the number of trips on a route using the same number of buses and operators. More reliable and frequent buses can often make transit a more attractive travel choice and increase overall ridership.
How do bus lanes improve public transit reliability?
Strategic bus lanes can greatly reduce bus delay and increase reliability for buses that travel through congested streets. Approximately 12,000 vehicles use Prospect Street on an average weekday, and using some of the street to allow the bus to bypass that traffic can help ensure that the bus keeps to its schedule. In this project, buses will get a headstart on Prospect Street at Webster Street and on Washington Street at Webster Street where the bus lanes are located. This will save time for over 13,000 average daily bus riders on these routes.
When the City implemented bus lanes on Broadway between Main Street and McGrath Highway, we saw an average of 60 seconds saved in travel times for buses along this segment of the street.
What are the parking impacts?
We anticipate removing 7 parking spaces on the east side of Prospect Street between Oak Street and Webster Avenue to make room for the new bus lane.
What other changes are being made?
We will be adding new camera equipment to each of the 3 major intersections within the project area, which will help the signals work better by adjusting green times to the amount of traffic on each approach. We will also be coordinating the signals during the busiest times of day, meaning that people driving from one intersection will get a green at the next intersection for certain traffic routes. This detection equipment, paired with timing changes, is intended to help everyone get through these intersections more quickly without compromising on safety. Please note that this camera detection equipment cannot see people’s faces and aligns with the City’s ordinance on privacy.
When are changes anticipated to be implemented?
Pending Traffic Commission approval at the July monthly meeting, the MBTA is anticipating installing the new pavement markings and traffic signal equipment between September and November 2026.
If you’re interested in learning about other MBTA Transit Priority projects, you can visit the Transit Priority Projects page.