Tag Archives: transit signal priority

No need to duplicate transit on Comm Ave

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NB: This got picked up on Universal Hub and there are a bunch of comments there. I’ll respond to comments in both forums, but probably here more. One note of clarification: I’m not saying that this should be the plan, but that it should be considered. Like much of the Commonwealth Avenue project, the planning process has been opaque and has had no public input. Also, this comment is a great illustration of what you could have.

The Boston Globe recently ran a story about proposed changes to Commonwealth Avenue. Of issue is that while Comm Ave is wide, it is not infinitely wide, and the changes will widen the transit reservation (mainly for safety for track workers, presumably this would also allow for wider stations), narrowing the rest of the road enough that the city is reticent to add cycle tracks, because it would narrow bus stops, and stopped buses would delay vehicles. (I’m just going to touch on the fact that there really shouldn’t be an issue with delaying traffic in favor of buses, bicyclists and pedestrians, but that’s not the scope of this post.)

What I am going to point out is that all of these issues could be mitigated by moving the 57 bus route and the BU buses to the center reservation of Comm Ave with the trolley tracks. This would result in the removal of bus infrastructure from the sides of the street—buses could instead stop at the same stations as Green Line trains. While this would be novel for Boston, it has been used in other cities, and while it could result in delays for transit riders, with better stations and transit signal priority, it would result in a better experience for all customers.

There are a variety of benefits from such a plan:

  •  Buses would move out of mixed traffic, resulting in fewer traffic delays for buses (especially at the busy BU Bridge intersection) and fewer conflicts between buses and traffic.
  • The duplicative infrastructure of having parallel bus and trolley stops would be eliminated. In their place, larger, more substantial stations could be built in the center transit median.
  • Instead of waiting for either a bus or a trolley, riders could board “whatever comes first” for short trips between Packards Corner and Kenmore Square, and riders wishing to go further east than Kenmore could take a bus to Kenmore and transfer down to a B, C or D car.
  • Removing bus stops would eliminate the conflict with buses pulling across the bike lanes when entering and exiting stops.
  • Removing bus stops would allow for more parking spaces to be added to the street. The number would be small—probably in the 12 to 18 range—but not negligible, and would assuage the (dubious) constant calls for more parking in the area.
  • In addition, there would no longer be issues with cars and taxicabs blocking bus stops, requiring buses to stop in the travel lanes.
  • Wider stations would better serve disabled users, with higher platforms better allowing wheelchairs and other disabled users to board and alight transit vehicles.
  • Narrower side lanes (parked cars are narrower than buses) would allow for more bicycle and sidewalk space, including the possibility of cycle tracks.
  • Without bus stops, there would be no need for bus passengers to get off of buses and cross a cycling facility.
  • With signal priority implemented, transit travel times through the corridor could be improved for bus and trolley riders.

The main reason to not to do this is that it hasn’t been done before. The cost to pave the trackbed—and to pave it well—wouldn’t be negligible, but since the entire corridor is under construction, it would be feasible. There would have to be some study to see if the number of vehicles would cause congestion in the transit reservation.

Additionally, there would have to be a specific signal to allow buses to enter and leave the corridor at each end of the corridor—especially the east end where they would have to merge back in to traffic. However, the 57 bus would only have to merge in to and out of the left lane since it then accesses the busway at Kenmore, which is in the center of the roadway. This could be attained with a signal activated by the approaching vehicle—again, a novelty in Boston, but by no means a procedure without global precedent.

The B line has 26,000 surface boardings, most of which travel to Boston University or through the campus and in to the tunnel. The 57 bus adds 10,000 more, and the BU Bus serves countless others. There are tens of thousands of pedestrians in the corridor, and thousands of bicyclists—it is one of the most heavily-traveled bicycle corridors in the city. Yet we are planning for cars—minority users of the corridor—first, when we should be planning for transit first (by far the largest user of the corridor by the number of passengers carried), then bicyclists and pedestrians. Cars should be an afterthought, put in to the plans after other users have been accommodated, not before. Of course, had the old A line never been converted to buses, Commonwealth Avenue would not host any MBTA services, and wouldn’t need any bus infrastructure. But that battle was lost 45 years ago.

The ignominious D Street light

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Much has been written about Boston’s Silver Line (including on this page). It’s certainly not rapid, but it is rather convenient: I made it from Kendall Square to Terminal A in 25 minutes. The problem? It should have been 23.

I’ve noticed in the past that the Silver Line experiences long waits at the D Street grade crossing after it exits the tunnel. On my ride yesterday, I decided to find out just how long, by means of Youtube:

The bus gets to D Street, and proceeds to sit there for not 30 seconds, not a minute, but just shy of a minute and a half! This is a major service failure. The scheduled time from South Station to Logan airport and back is 45 minutes, meaning that if the bus loses 1:30 each time it crosses D Street, 7% of the route time is spent waiting for a traffic light. For the SL2 line, which is a 25 minute round trip, 3 minutes is 12% of the total operating time!

There’s this thing called “transit signal priority” which could be employed to eliminate these wait times. A sensor could be placed just outside the WTC station (and a similar one on the inbound run) which would be tripped when the bus passed by (there are already sensors which detect the bus and raise gates when the pass, and which close barriers should someone attempt to drive in to the tunnel). This would give 15 seconds to flash the don’t walk sign and change the light, allowing the bus to proceed through the intersection at full speed. Traffic would not be dramatically impacted since there light would only be red for a few seconds when the bus passes, and an algorithm could be put in to place to assure the green cycle for traffic was long enough to avoid backups (but not, you know, not 90 seconds when very few cars pass through; see above).

Transit signal priority (TSP) is not very expensive; even at the high bound it costs $35,000 per intersection. Ridership on the SL1 is, give or take, 8,000 per day. This means that in a year, for one penny per passenger, trip lengths could be reduced by more than a minute. This should be implemented immediately.


What’s more, this would result in reduced operation costs for the MBTA. Buses cost somewhere on the order of $100 per hour to operate. Even if the average time savings per bus was only 30 seconds, this would equate to 4.5 hours of operating time per day, or a $450 savings. Assuming a $35k cost for TSP implementation, it would pay for itself in 78 days—two and a half months.

The argument could be made that these times would just be built in to schedule padding at the end of the route and savings would only be from the reduced power use related to not stopping and starting. But, especially on the SL2, saving a couple of minutes could be used to decrease the overall route time and increase service, something the Seaport District desperately needs. At rush hour, decreasing the trip time from 25 to 23 minutes would allow headways to drop from 5:00 to 4:36—a capacity increase of 8%—without any additional cost. This would allow for 3 additional round trips at rush hour, or 75 additional minutes of service, which would save the T $125. By this metric, the payback would be $250 per weekday, and take 140 weekdays to pull in to the black. That’s 7 months. After that, it’s gravy.

(Another improvement: extending overhead wires along the whole of the SL2 route would allow the buses to operate without a change of power twice per trip; combined with the savings at Silver Line Way this might allow service to operate at 5 minute headways with 4 buses—a dramatic savings, albeit one with a higher initial capital cost.)

There is no logical reason that transit signal priority should not be immediately procured and installed at D Street. There is no need for a time-consuming review process; the benefits are clear and any disruption to traffic will be far less than the current disruption to the traveling public. While the Silver Line is still hobbled by a convoluted route system, low capacity, slow tunnel speeds, traffic and a poorly-designed power switch (often requiring the operator to exit the bus and manually raise the trolley poles), this inexpensive change would be a good start to dramatically improve service.