Street racing is a form of unsanctioned and illegal auto racing which takes place on public roads. Street racing can either be spontaneous or well-planned and coordinated. Spontaneous races usually occur at intersections where two cars stop at a red light before they begin racing. Well coordinated races, in comparison, are planned in advance and often have people communicating via 2-way radio/citizens' band radio and using police scanners and GPS units to mark locations of local police hot spots. (See participants, below). Street racing is reported to have originated prior to the 1930s due to alcohol prohibition in some parts of the United States. At the time smugglers of unrefined and illegal alcohol would try to find ways to make more power and achieve better handling from their engine and suspension. Aside from being the basis of stock car racing, this became common after the war, and as a result, it is credited as being the origin of drag racing as well. Opponents to street racing cite a lack of safety relative to sanctioned racing events, as well as legal repercussions arising from incidents, among street racing's drawbacks. Most duels are drag races.