85 Mph Speedometers
On September 1, 1979, in a regulation that also regulated speedometer and odometer accuracy, the National Highway Traffic Safety Administration (NHTSA) required speedometers to have special emphasis on the number 55 and a maximum speed of 85 mph (137 km/h). However, on October 22, 1981, NHTSA proposed eliminating speedometer and odometer rules because they were "unlikely to yield significant safety benefits" and " highlighted '55' on a speedometer scale adds little to the information provided to the driver by a roadside speed limit sign."
Read more about this topic: National Maximum Speed Law