Recently, in an effort to make D.C.’s WMATA feel good about itself, Boston’s T, specifically the Red Line, was pretty much broken due to a derailed train that wiped out much of the signaling infrastructure. As with so many unplanned natural experiments about the importance of mass transit, driving turned into a nightmare (boldface mine):

This could compel more people to hop into their cars or explore options such as Uber and Lyft. So suddenly this isn’t just a problem for transit customers, but for anyone driving into the city from the south.

We already started to see this happen on Tuesday, when gridlock reigned because news of the derailment came early enough in the morning that a bunch of riders decided to get in a car. (I did, and I was stuck in more than an hour of bumper-to-bumper congestion on Milton and Quincy roads.)

…The Northeastern University emeritus professor has compiled statistics from the state showing that drivers going northbound from the Braintree split on Interstate 93 during the morning rush hour travel, on average, at 10.3 miles per hour. (And that’s without an accident or construction.)

Let’s play out what would happen if just 100 more cars got onto that artery during the morning commute into Boston. According to Bluestone’s calculation, the expected average speed would drop to 8.8 miles per hour. That amounts to a 15 percent increase in commute time.

“A bike rider would go twice as fast as the typical commuter on the Southeast Expressway during rush hour,” Bluestone said.

Add bike lanes to the highway? Sounds ridiculous, but that might be faster than fixing the T.

Even if you don’t ever use mass transit, in many metro areas, if mass transit fails, then driving becomes much, much worse. You are the traffic.