2 minute read
Optimize System Speed and Capacity
from BRT Playbook
by Sauced Media
OPTIMIZE VEHICLE SIZE AND FLEET SIZE
Optimizing the BRT bus size and fleet size is an iterative process. Standard 40-foot buses or 60-foot articulated buses are likely the most appropriate options for the Everett‒Boston corridor. The larger the vehicle, the smaller the required fleet. Given the same fleet size, larger vehicles tend to have lower operating costs but also translate into lower frequency and longer wait times for passengers. MBTA will need to evaluate these trade-offs when optimizing the vehicle size needed for this corridor.
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The fleet size is determined by the number of vehicles needed to serve the maximum passenger load on the critical link during peak time. Since BRT reduces bus delay from traffic congestion and other sources, buses on the routes can be used more efficiently, providing more service with the current fleet size.
To be competitive with other modes, the BRT system needs to be designed with sufficient capacity and speed. As the passenger demand and fleet size increase, so does the potential for bottlenecks and operational snags along the corridor.
DETERMINE SERVICE FREQUENCY
The greatest benefit to bus travel time along Broadway is increased service frequency. While there is a benefit from speeding up buses and eliminating transfers, these do not impact passengers as much as simply running buses more frequently. However, these are intertwined: Faster and more reliable buses can run more frequently. Faster buses simply cover the same route in less time, allowing them to provide more trips, while more reliable buses require less schedule recovery time, allowing the same improvement. And up to a point, increasing vehicle frequency on the corridor will increase the capacity.30
Service frequency makes the BRT more viable for people who need to make a transfer. When people make a transfer, the utility of their trip is only as good as the least-frequent mode: Making the bus as frequent as the Orange Line makes it as useful as the Orange Line (see Table 1).
Along Broadway, several interlined bus routes currently combine to provide bus service every six to 15 minutes between Everett and Sullivan Square, depending on time of day (see Understand Existing Public Transport Network). Along the Broadway corridor, ITDP recommends the new BRT routes combine to provide service at least every three to six minutes. Along Rutherford Avenue, the BRT service plan should aim for service headways of 10 minutes, with more service as demand requires. The fleet size will determine the minimum service frequencies.
