The rules of the system have been continually negotiated by the community since the practice began in the early 1970s: Don't speak unless spoken to. Don't eat or drink without the driver's permission. Don't talk on the phone. Most important, under no circumstances are you permitted to snore if you fall asleep.

But now passengers and drivers have to settle payment of the toll, igniting passions, dividing the community and causing some to even question the value of the casual carpool in the first place.