David D. Friedman's The Machinery of Freedom proposed a similar system (which he referred to as "jitney transit") in the 1970s. However, his plan assumed that passengers would be expected to pay for their transit, and that security measures such as electronic identification cards (recording the identity of both driver and passenger in a database readily available to police, in the event one or both parties disappeared) would be needed in order for people to feel safe. Although slugging is informal, ad hoc, and free, in 30 years no violence or crime was reported from Washington D.C. slugging until October 2010, when former Sergeant Major of the Army Gene McKinney struck one of his passengers with his car after they threatened to report his reckless driving to the police.
