Traffic Impact Analysis

The cities of Everett and Boston and the MBTA should prioritize corridor design elements that can help increase operating speeds:

Platform-level boarding (a Basic BRT Element; see Appendix B) requires minimizing the horizontal and vertical gap, or a bridge plate;

Bus-station docking procedure. A slow, careful approach to the station increases the dwell time and slows down service frequencies. Mechanical docking aids such as Kassel curbs, a rub rail, or Carey fingers (compressible rubber fingers along the outside edge of the station platform) can reduce the station‒bus gap and speed up docking;

Off-board fare collection (a Basic BRT Element, see Appendix B);

More and wider bus doors. The BRT buses should include as many wide doors as possible (see Fleet/Vehicle Selection).

CONSIDER MULTIPLE SUB-STOPS

In higher-capacity systems, some or all stations may include multiple docking bays or places where multiple buses can dock on the same side of the station/direction of travel. This is especially helpful where multiple BRT routes converge. The additional bus docking bays can add walking time and confusion for passengers if not designed and signed well. The demand on the Everett‒Boston corridor likely obviates the need for multiple sub-stops at most stations. An exception might be Sullivan Square, where several BRT routes likely intersect the corridor, such as connections to downtown Boston and Cambridge/Somerville if these destinations aren’t served by routes originating in North Everett.

CTPS and the cities of Everett and Boston should explore the operational benefits of multiple sub-stops at a Sullivan Square BRT station, as well as the infrastructure requirements. Microsimulation could help illustrate what impact adding a docking bay at Sullivan Square station has on corridor capacity and speed.

Traffic engineers will need to assess how the proposed changes to the corridor to accommodate BRT will impact the other modes using the transport network. This will be an iterative process. As the BRT corridor design is resolved, the traffic impact analysis can be refined from a planning level, to operational, to finally micro simulation of individual intersections.

There are three primary reasons to analyze the traffic impact of the BRT:

1

To understand the impact of the general traffic on BRT operations. Congestion could block intersections and impede the movement of the BRT buses.

2

3

To assess the impacts of the BRT on general traffic. Changes to the street cross-section and signalization can impact general traffic. Traffic engineers should assess all the ways a BRT corridor affects other road users, including:

a. Reallocation of travel lanes to BRT b. Removal of on-street parking c. Narrowing of travel lanes to accommodate BRT lanes and stations d. Changes to signal timing, including TSP, which will shorten the green time available for general traffic, especially cross traffic e. Left-turn restrictions across the BRT lanes and rerouting turning movements f. Traffic diversions to parallel streets g. Removing local buses from mixed-traffic lanes h. Increased pedestrian and bicycle activity at BRT stations i. Improved general traffic flow at corridor bottlenecks such as

Sweetser Circle, Sullivan Square

Massachusetts environmental review process will likely require a traffic impact analysis to demonstrate the environmental impacts of the BRT corridor.31

Traffic engineers at the cities of Everett and Boston should identify impacts of the BRT corridor on the transport network and recommend mitigation measures, including street design, signalizations, and parking provision/ policies.