The view from your L train shuttle bus, starting next year Victor J. Blue/Bloomberg via Getty Images

On any given weekday, the Williamsburg Bridge is clogged with traffic. As one of just two toll-free East River crossings — along with the Manhattan Bridge — that provide commercial vehicles with direct access to Lower Manhattan from Brooklyn and Long Island, the Williamsburg Bridge is a crucial route for trucks and large vans. During rush hours, bridge traffic not only makes the span itself a mess, but packs streets on either end for dozens of blocks.

It is into this gridlock that the MTA and DOT plan on sending up to 80 buses per hour during the L train shutdown to shuttle displaced L train riders across the river. Four Select Bus Service routes created just for the shutdown will take commuters from Williamsburg to subway stops in lower Manhattan and vice versa.

“Buses will be an important piece of the puzzle,” DOT commissioner Polly Trottenberg told the City Council during a hearing on the shutdown plans last month. The MTA predicts approximately 17 percent of displaced L riders, or up to 4,200 riders per hour and more than 30,000 per day, will use these shuttle buses, while the rest will take to other subway lines, and to a lesser extent bicycles or ferries.

Yet DOT has opted not to put a dedicated bus lane on the bridge itself — meaning buses will have to compete with existing commercial traffic. Further, the city plans to institute only limited bus lanes on the approaches, which transit experts warn could doom the entire shuttle bus system.

J.P. Patafio, vice president of the surface transit division of Transit Workers Union Local 100, which represents the city’s bus drivers, says forcing buses to compete with commercial vehicles for space on a narrow bridge is a recipe for disaster. “The Williamsburg Bridge is a particularly tricky bridge because it isn’t a modern bridge with wide lanes,” he says. “If you don’t give a bus a dedicated lane, I don’t care what they say, you’re gonna have traffic backing up in Manhattan because it’s going to be backing up on the bridge” in the afternoon rush; during the morning rush, meanwhile, Brooklyn “is going to be a mess.”

Walter Hook, a New York City–based urban planner for BRTPlan, which specializes in implementing Bus Rapid Transit routes, tells the Voice that the risk is “very high” that the Williamsburg Bridge will be “totally clogged” during the shutdown.

“We met with DOT and we walked them through it,” Hook recalls. “And we said that these buses are gonna go two miles per hour.”

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When the L train stops running under the East River next year, the only vehicle restriction Mayor de Blasio’s DOT plans to place on the Williamsburg Bridge is an HOV-3 rule: All cars must have at least three people in them. Commercial vehicles and ride shares — which are expected to soar in popularity during the shutdown — will still be permitted at all times, even during peak commuting hours. (Ride shares will have to abide by the HOV-3 restriction.) These restrictions are far less stringent than the ones being put in place on 14th Street between Third and Eighth avenues, where DOT is making the entire road bus-only from 5 a.m. to 10 p.m. seven days a week.

Every aspect of the mitigation plan — from the extra subway service to the shuttle buses to the ferries — has to run smoothly because even the slightest hitch could throw the whole plan into disarray. To wit: DOT found that if only three percent of projected 14th Street bus riders opted for For-Hire Vehicles instead, the entire benefit of the busway would be negated by increased congestion on the surrounding streets.

“DOT’s traffic studies show that the HOV 3+ lane will provide an adequate flow of buses over the bridge,” a DOT spokesperson told the Voice in an email. “If any adjustments are needed during the shutdown, we will make them accordingly.”

Transit activists have been sounding the alarm about the traffic on the bridge since before DOT’s plan was even announced in December. While the MTA and DOT have held dozens of public meetings about the shutdown over the last several years, including two highly-publicized town hall meetings in May that largely focused on the Manhattan bike lanes and 14th Street busway hours, some experts have continued to warn that the biggest flaw is the lack of a bus-only lane on the bridge and its approaches. Yet transit authorities have never publicly discussed a bus lane on the bridge in any detail.

“We don’t believe [DOT has] done a sufficiently rigorous study that that road won’t be totally congested,” Hook tells the Voice. In January, Hook co-authored a study on the mitigation plan, which was released in partnership with Transportation Alternatives. The analysis concluded there are significant gaps: Although DOT will put in some form of bus lanes on key bridge approaches, the bus lanes owill not have turning restrictions for other vehicles, which will clog the lane as they wait for pedestrians to cross. Also, the two bus routes from the Bedford Avenue L train stop will have to connect to the bridge via Roebling Street and Bedford Avenue, which will have no bus-only lanes.

“In my view, they’re trying to come up with a proposal with middle ground,” Hook surmises regarding DOT’s mitigation plan. He adds that DOT’s analysis did not formally model more aggressive plans, such as a longer busway in Manhattan extending along most of the 14th Street bus route instead of just from Third to Eighth avenues. “They should approach it from a technical perspective. How are they going to do this?”

Painfully slow bus speeds would be a worst-case scenario for everybody involved. Frustrated commuters would abandon the buses for other modes of transit, such as nearby subways or ferries — which are already projected to be at or above capacity during the shutdown. Even more catastrophically, others may resort to app-based services such as UberPool, Lyft Line, and Chariot to meet the HOV-3 restriction, which will only exacerbate the traffic problems on the bridge.

The traffic mess is further complicated the Williamsburg Bridge’s peculiar layout. The bridge has eight lanes of traffic, four in each direction. Above the river, those four lanes split into inner and outer two-lane segments. The lanes on the bridge are narrow, so buses will need to straddle multiple lanes (as some commercial vehicles already do). Further, because of height and weight restrictions on the inner segments, buses and trucks (along with vehicles making right turns after the bridge) will be directed to the outer lanes during the shutdown. If the lanes are too narrow for commercial vehicles and buses to coexist side by side, the outer segments could essentially become one-lane roads, while ride-share vehicles and small commercial vans would have the inner lanes all to themselves.

DOT officials indicate that the narrow bridge lanes are one reason dedicated bus lanes were rejected: If buses take up double lanes, that would mean removing cars from half of the bridge. But Hook says the only places the lanes are too narrow are at a pair of “choke points” by the towers, and the lanes could safely merge there to allow buses priority without completely stopping car traffic in the adjacent lane.

Patafio emphasized the need not only for dedicated bus lanes on the bridge, but for turn-restricted lanes leading up to the bridge itself. This would keep buses moving in otherwise congested areas while also making enforcement easier, as police could pull any vehicles that aren’t buses out of those lanes before they get on the bridge. (It remains an open question exactly how enforcement of the HOV-3 restriction will work under the DOT plan.)

This would also be an inexpensive solution. Patafio, a former Brooklyn bus operator, cited a recent successful trial in Boston that converted a parking lane into a 1.2-mile bus lane using only traffic cones and a few signs. A run time that could previously take up to a half-hour for buses to traverse was shaved down to ten minutes or fewer. (The city has since made the lane permanent.) He sees a similar model working well during the shutdown, especially since it can be deployed quickly if and when all parties involved agree that it’s necessary.

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As with when the city released its traffic analysis for 14th Street, the HOV-3 solution appears to be an attempt at a middle ground between Doing Everything and Doing Nothing — when the L train shutdown is such a nightmare scenario that we need to do everything, or close to it, to make it remotely manageable.

Patafio knows that more bus-only lanes would result in uproar from drivers, as well as from businesses that might not be able to get deliveries as conveniently. But he views this as a necessary evil during the biggest transit challenge the city has faced in years.

When many subways were shut down following Hurricane Sandy, he notes, the MTA implemented free shuttle bus service from Brooklyn to Manhattan. The lines for the buses stretched for blocks, but DOT established dedicated bus lanes on the Williamsburg and Manhattan bridges to keep them moving.

Patafio believes a similar all-in effort is necessary for the L shutdown: “If they don’t give us what they got in Manhattan on 14th Street and they don’t put it in Brooklyn and make some hard decisions, then I think you’re gonna have a whole shitload of traffic.”

Councilmember Antonio Reynoso, who represents Williamsburg and Bushwick, recalls that a bus-only lane across the bridge was “one of the first things we asked” DOT about the shutdown plan. He says DOT assured him the HOV-3 restriction would reduce traffic enough that a busway won’t be necessary. He’s trusting DOT on that, at least until the shutdown begins and he can see for himself. But, he adds, DOT told him there are contingencies in place in case things don’t go according to plan, and one such contingency may be a bus lane.

Nevertheless, Reynoso is reminding himself to be calm and work with the powers that be to create the best plan for his community and the city as a whole. “The first week, maybe a month, are going to be a disaster,” Reynoso cautions, as everybody adjusts to their L train–less reality. “I don’t think any of us are prepared for how significant this is going to be.”