speed limit warning

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.
The first numeric speed limit for mechanically propelled road vehicles was the 10 mph (16 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. The World Health Organization (WHO) identified speed control as one of a number of steps that can be taken to reduce road casualties. As of 2021, the WHO estimates that approximately 1.3 million people die of road traffic crashes each year.
Authorities may also set speed limits to reduce the environmental impact of road traffic (vehicle noise, vibration, emissions) or to enhance the safety of pedestrians, cyclists, and other road-users. For example, a draft proposal from Germany's National Platform on the Future of Mobility task force recommended a blanket 130 km/h (81 mph) speed limit across the Autobahnen to curb fuel consumption and carbon emissions. Some cities have reduced limits to as little as 30 km/h (19 mph) for both safety and efficiency reasons. However, some research indicates that changes in the speed limit may not always alter average vehicle speed.
Lower speed limits could reduce the use of over-engineered vehicles.

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