An article in the Washington Post over the weekend inspired me to look into "slugs" and "slug lines" around DC. This is an amazing self-organized transit solution.
Slugging is a term used to describe a unique form of commuting found in the Washington, DC area sometimes referred to as "Instant Carpooling" or "Casual Carpooling". It's unique because people commuting into the city stop to pickup other passengers even though they are total strangers! However, slugging is a very organized system with its own set of rules, proper etiquette, and specific pickup and drop-off locations. It has thousands of vehicles at its disposal, moves thousands of commuters daily, and the best part, it’s FREE! Not only is it free, but it gets people to and from work faster than the typical bus, metro, or train. I think you'll find that it is the most efficient, cost-effective form of commuting in the nation.
Thousands of commuters everyday. Organized by word of mouth, social norms and supported by a simple website. The website reinforces the norms and rules (includes reputation system, lost and found, message boards). The network teaches new comers how to use the system and is reinforced by the redundancy of lost of rides and riders with a back end of solid alternative "official mass transit."
It is truly network-centric.