Northern Virginia has an interesting hitchhiking system called slugging. Drivers who want to use the HOV lanes, but don’t have the required three passengers, pick up “slugs” at various lots south of DC. The occupants allow the use of the HOV lane and get both drivers and passengers there much faster. No money is exchanged and there are some simple rules, such as no talking unless the driver initiates it. This form of transport has been around since 1975 and it is evidently as fast or faster than taking the bus and significantly faster than driving as a single person in traffic. A couple of my colleagues slug to work w/o any significant problems.
It is interesting that such a cooperative market has grown up w/o outside regulation. Local governments accept it and welcome it as a way to reduce congestion. There have been occasional calls for the government to somehow regulate the system, but that would probably make it collapse. If it ain’t broken …
More information is at this link.