Silver Line is flawed – but fixable

Improve existing system before adding shuttles, ferries, or gondolas

WITH THE 7.7 MILLION SQUARE FEET of development at Seaport Square approved by the Boston Planning and Development Agency, and a multitude of other development projects filling in further and further from the waterfront, it has become abundantly clear that the current state of Seaport District transit is inadequate to handle present, let alone future, demand.

At Skanska’s 121 Seaport location alone, 400,000 square feet of new office space will house 1,400 workers, of which fewer than 30 percent are projected to drive. The others will walk, bike, and take transit, and while the high non-car mode share is undeniably a positive development, the existing transit system in the area is already overcrowded. Confronted with these issues, a variety of proposals have emerged to solve the capacity crunch — expansion of the fleet of private shuttles from North Station, new ferry routes in the inner harbor, and even a $100 million gondola from South Station to Drydock Avenue have all been proposed. But looking for new, innovative solutions overlooks the best system we have for moving commuters into the district – the flawed, but fixable, Silver Line.

After having some of the lowest ridership per station in the entire MBTA for its first 10 years, rapid development along Seaport Boulevard has caused a spike in Silver Line utilization. With current service levels, this results in bad frequency, slow trips, and users being left behind on the platforms due to overloaded buses. While the existing Silver Line is badly overstressed, the “bones” of the line – the physical infrastructure – are far superior to any proposed alternative system for Seaport transit.

The Silver Line Waterfront service runs in a grade-separated transit tunnel, arcing from South Station to Seaport Boulevard and then back south toward the Convention Center. The stations are large, with arrays of fare gates and full-length mezzanines. The pedestrian visibility is good, with multiple station entrances to maximize the walkshed of each station. Service is operated by dual-mode busses that operate emission-free in the tunnel, then turn on diesel engines to continue to Logan or Drydock Avenue.

At the other end, at South Station, riders can transfer free of charge to the Red Line via an indoor, accessible station complex, with the commuter rail on the level above. The flaws of the existing system come not from fundamentally bad infrastructure, but from low capacity and frequency. Implementing two simple enhancements to the Silver Line should be the first priority of those who want better waterfront transport access. For less money than a gondola or ferry, and with more equitable access than private shuttle buses, Boston can and should build a higher-capacity, faster Silver Line.

The first fix simultaneously makes trips faster, increases frequency, increases capacity, and costs negative dollars. On the outbound route to Logan, Silver Line busses must follow a complicated backtracking route to enter the Ted Williams Tunnel. However, there exists a much faster entrance. Directly after leaving Silver Line Way, SL1 busses could simply make two right turns and find themselves on a bus-only on-ramp, cutting minutes off their trip time.

The dedicated on-ramp bypasses the bulk of tunnel traffic, which is at the previous ramps, creating an analog version of bus priority. Unfortunately, the Massachusetts State Police have taken over this ramp and refuse to provide access to the MBTA. There is no credible reason for preventing use of this ramp by MBTA busses. (When portions of the tunnel access points to the Williams Tunnel were closed following the tragic failure of a portion of the tunnel ceiling in 2005, MBTA busses were allowed to use the ramp.)  The record shows that there was no impediment to the operations of the State Police because of this shared use.

The most cost effective improvements should be pursued first, and convincing the State Police to let the T use a ramp that already exists should cost nothing at all. Gov. Charlie Baker could make this happen with a meeting and the stroke of a pen. If implemented, SL1 busses would reach Logan and complete their trips faster, which would boost frequency along the entire route as buses returned early. Since capacity at peak times is directly proportional to frequency, the routing change will help solve one of the biggest problems with Seaport transit for no additional cost.

The second fix is perhaps the most fundamental one. The Silver Line is too popular for its current fleet of buses, so the T should order more. The infrastructure of the tunnel, with massive stations and long platforms, is clearly capable of handling increased service. In fact, the original conception of the line involved platoons of three busses traveling together. While such an expansion of the line’s fleet would have been wasted during the Silver Line’s first decade of operation, the ongoing boom in development, especially peak-oriented office buildings, has substantially overstressed the existing system.

While the dual-mode buses in current use are expensive and hard to source, the most overcrowded portion of the line, the waterfront tunnel, can and has been served by simple electric trolleybuses such as those used in Cambridge. The MBTA should promptly procure an expanded fleet, freeing up dual mode buses for SL1 and SL2 service. If this capacity is still not enough, the T could electrify the entire SL2 service, from its existing changeover at Silver Line Way to Drydock Avenue, and use all of its specialty buses for airport service. While neither investment is free, electric trolleybuses cost on the order of $1 million per unit, meaning that with only Seaport Square’s planned $2.5 million per year contribution towards district transit, rapid fleet expansion should be possible.

If the first two solutions still leave seaport transit overcrowded (and there is plausible reason to believe they may, at least in the long term), then the Massachusetts Department of Transportation and the city of Boston should look at higher-cost capital fixes. The largest of these deals with the single point where the Silver Line Waterfront service intersects with private traffic – the D Street light. Existing service frequently has to wait for up to a minute to cross the intersections, and the existing light only permits two buses per direction per cycle to pass.

Future frequency increases risk forcing every bus to wait at least one full cycle, a particularly extreme version of bus bunching. While the complexity of construction would likely force a closure of the existing Silver Line service for several months, if the line truly begins to exceed the capacity bought with the two previous improvements, the MBTA should bite the bullet and construct a bus tunnel under D St, rising up to meet the existing Silver Line Way Station. The cost, likely at tens of millions of dollars, is far higher than previous solutions, and should thus be pursued after other organizational and fleet changes. However, the improvement leverages the existing, much larger investment in the transitway tunnel, and is thus likely to be more cost effective than any new transit system, which must reinvent the entire route.

Of course, there are other bus-oriented transit fixes that must be considered to bring transit mobility in the Seaport District to the place it ought to be. The MBTA has committed to improving service on the 7 bus. The advocacy group TransitMatters has proposed a new bus rapid transit service that would connect South Station to the Boston Convention and Exhibition Center, Logan Airport, the Flynn Maritime District, and South Boston along the First Street corridor, taking pressure off the existing Silver Line service and providing better bus transit in a currently underserved (and increasingly residential) corridor. These improvements ought to go forward as necessary complements to the Silver Line enhancements I have proposed here.

Meet the Author

Ted Pyne

Leader of outreach and recruitment efforts to college students, TransitMatters
While the Silver Line in its current form is obviously inadequate, its inadequacy comes from insufficient capacity, not a fundamentally flawed design. Seaport planners and developers should recognize its potential, and push for prompt, cost-effective enhancements to the Silver Line over ferries, gondolas, or private shuttles.

Ted Pyne is a member of TransitMatters and leads its outreach and recruitment efforts to college students in Massachusetts.