CentralNotice From Wikipedia, the free encyclopedia Jump to: navigation , search "Double nickel" redirects here. For the Interstate Highway in the central United States nicknamed "double nickel", see Interstate 55 . 55 mph speed limit sign being erected in response to the National Maximum Speed Law. The National Maximum Speed Law ( NMSL ) in the United States was a provision of the Federal 1974 Emergency Highway Energy Conservation Act that prohibited speed limits higher than 55 miles per hour (90 km/h). It was drafted in response to oil price spikes and supply disruptions during the 1973 oil crisis . While Federal officials hoped gasoline consumption would fall by 2.2%, actual savings were estimated at between 0.5% and 1%. The law was widely disregarded by motorists, and some states opposed the law, but many jurisdictions discovered it to be a major source of ...