Speed limits on road traffic, as used in most countries, set the legal maximum speed at which vehicles may travel on a given stretch of road. Speed limits are generally indicated on a traffic sign reflecting the maximum permitted speed, expressed as kilometres per hour (km h) limit introduced in the United Kingdom in 1861.
Speed limits are frequently introduced for health reasons with a goal to improve road traffic safety and reduce the number of casualties from traffic collisions. There is a relationship between speed and health impacts, whereby it has been posited that a 5% increase in speed is linked to a 10% increase in injury, and a 20% increase in deaths. Speed limits tend to be stricter in areas with more pedestrians, in particular those frequented by children.