One way to reduce accidents is to set speed limits for each road. The speed limit takes into account the density of population in that area, the topography of the road—features such as hills and bends—and the crash history of a given road. The speed at which traffic actually tends to travel is also figured in.

Almost all countries now post speed limits of some kind, although enforcement may be minimal or nonexistent. In some cases, the speed limits are so high as to be meaningless. Both Austria and the United Arab Emirates have highway speed limits of 159 km/h (99 mph). Many sections of Germany’s autobahns (freeways or motorways) have only advisory speed limits. In most places the law requires that drivers of cars and motorcycle riders be able to stop their vehicles within the line of sight, which represents a speed limit of sorts

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