No single- or two-passenger cars on the Williamsburg Bridge during the morning or afternoon rush. A new ferry route. Extra turnstiles in some Brooklyn subway stations. The packed lanes of 14th Street in Manhattan given over solely to buses. Twice as many bicyclists whizzing over the East River from Brooklyn.

Welcome to the L train shutdown.

The first details of the sweeping and complex workaround for the April 2019 closing of part of the L train line were released on Wednesday by the agencies tasked with remapping the daily human migration during the temporary absence of one of New York City’s busiest lines. It was the most comprehensive look so far at plans to reroute more than 400,000 daily riders affected by the 15-month closing of the line’s tunnel beneath the East River, which is in desperate need of repair after flooding during Hurricane Sandy.

The L line has helped fuel some of New York City’s fastest growing neighborhoods, like Bushwick, Greenpoint and Williamsburg in Brooklyn. It will be closed from the Bedford Avenue stop in Brooklyn to its terminus on Eighth Avenue in Manhattan.

The New York City Department of Transportation and the Metropolitan Transportation Authority jointly released the preliminary plans for coping with the disruption. They were frank: Rerouting the 225,000 people who take the train beneath the East River each day, the 50,000 who use it just to travel across Manhattan, and everybody else who rides the line, will not be easy.