What could happen if the L shuts down, in maps

Gothamist ruled the news late last month, scooping the New York media behemoths when it somewhat confusingly reported a blind item about the L train potentially being shut down for repairs. L Train Service Between Brooklyn & Manhattan May Be Shut Down For Years, the headline blared. Large swaths of Brooklyn got worried.
“A disruption of epic proportions potentially looms for New Yorkers who rely on the L train to get in and out of Manhattan,” the article, which has become taken as the final word in many a Brooklyn conversation, said. “The project to repair the Canarsie Tube is projected to take three years, and the MTA is considering shutting down service between Manhattan and Brooklyn entirely to get it done, according to MTA sources familiar with the initiative.”
So Brooklyn’s mapping mavens, CartoDB, took a minute to think critically and find out what affect an L train shutdown would actually have.

About 200,000 people cross from Brooklyn to Manhattan on the L train each day, according to the MTA (or 300,000, according to Gothamist). If there’s a complete shutdown, the MTA will likely increase trains on other, nearby lines, like the JMZ and G, and also offer shuttle bus service between Brooklyn and Manhattan.
CartoDB created some assumptions about walking time to proposed bus stops and population densities, and found that for 125,000 of those 200,000 affected, it would make more sense to walk to the nearest available subway than it would to take a shuttle bus, even with no traffic. Estimating a bus trip of 28 minutes (which, over the Williamsburg bridge in the morning, like, good luck) the team at CartoDB found that the bus would be more convenient for 53,000 people.
“The challenge that we realized was that the shuttle is the best option for almost 75,000 riders per day,” CartoDB wrote. “Given large buses with 65 passengers this would still take 1154 bus trips per day, or a bus every minute and a half or so. That’s pretending there are only completely full buses or rush hours. To handle this capacity they’d have to build a new bridge.”

What CartoDB’s findings boil down to is that the complete shutdown scenario just sucks.
For three quarters of L riders, the replacement service is worse than just walking to a farther subway. And for the one quarter of riders for whom a replacement bus would be shorter, the times to get into the city are still pretty gnarly and possibly still too optimistic.
Optimism and pessimism are things which generally figure into this story. If you sensed some skepticism in our discussion of the Gothamist report, well…
Look, the Times and the Post have the best sources you can reasonably have inside the MTA. Both of them got scooped by a features editor at Gothamist. The Times followed the Gothamist bombshell with a decidedly toned-down story titled, Tunnel Repairs Could Disrupt L Train in Coming Years. It quoted an MTA spokesman (I guess none of their sources could corroborate the Gothamist story?!) who said, “The work has to get done. … There is no way around it. Unfortunately, the L is unique in that there is such heavy ridership in an area that has so little redundancy from other subway lines.”
The Post followed up as well and did the best they could: L train might shut down Manhattan-Brooklyn service in hipster nightmare but ultimately quoted the same spokesman, Adam Lisberg. Their sources must have been otherwise occupied as well.
One thing we do know is that there’s damage to the tunnel from Superstorm Sandy and work will be required to fix it. Speculating here, there’s also the possibility that the MTA is floating a worst-case scenario so that the plan they come out with doesn’t seem so bad in comparison. We don’t know. There’s work to be done, and that work, whether it’s a complete shutdown, a weekend shutdown, or the use of one of the two tunnels only, will suck for riders. Nothing is expected to start before 2017.