The trial passes are only guaranteed to cover this November, and you'll have until October 31st to buy one. Also, don't count on getting a pass: there are "limited quantities," and you'll have to commute in Atlanta, Chicago, Los Angeles, Miami, San Diego and Washington, DC.

Lyft's effort comes just after Uber handed out a $79 card that gave New York City commuters unlimited UberPool rides for a month. It's not certain how Lyft manages to undercut its biggest rival to that degree, but that's what a test is for. Clearly, it's hoping that there will be enough riders to make the economies of scale work. As it is, Lyft may well want this transit pass model for its eventual fleet of self-driving cars. When it can run cars around the clock for relatively little cost, it only makes sense to keep those vehicles as busy as possible.