I think ride "sharers" with a single rider are strictly worse. That driver is going to drive a non-zero amount of miles to pick up his next passenger. Those mil

I think ride "sharers" with a single rider are strictly worse. That driver is going to drive a non-zero amount of miles to pick up his next passenger. Those miles are traffic that wouldn't exist if the two passengers drove themselves. The only thing ride sharing reduces is parking requirements, unless the ride sharing is truly carpooling.