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) or miles per hour (mph) or both. Speed limits are commonly set by the legislative bodies of national or provincial governments and enforced by national or regional police and judicial authorities. Speed limits may also be variable, or in some places nonexistent, such as on most of the Autobahnen in Germany.
A road sign shows maximum and minimum speed limit for different types of vehicle on expressway in China. Speed limit signs are shown in kilometres per hour.
Historic New Hampshire speed limit sign
In 1920 a pastor was fined US$10 for "overspeeding his machine ... at a rate greater than 25 mph (40 km/h) ... in what appeared to be a reckless manner."
Example variable speed limit sign in the United States, in mph
The kilometre per hour is a unit of speed, expressing the number of kilometres travelled in one hour.
A car speedometer that indicates measured speed in kilometres per hour.
Speed limit sign in the Republic of Ireland, using "km/h."
