Speed limitUnited States

A speed limit is the maximum legal speed permitted on a road, lane or within a designated area. It does not require drivers to travel at that speed.

A speed limit is commonly displayed as a number on a regulatory traffic sign. General limits may also apply automatically because of the country, road category, vehicle type or surrounding area, even when no speed-limit sign is present.

No. It is the highest speed legally permitted under suitable conditions. Drivers must reduce their speed whenever travelling at the limit would be unsafe.

Yes. Drivers should travel more slowly when required by traffic, weather, visibility, road conditions or nearby vulnerable road users. Driving unnecessarily slowly may nevertheless be prohibited when it obstructs normal traffic.

Not always. Lower limits may apply to heavy vehicles, buses, vehicles towing trailers, novice drivers or other vehicle categories. The lowest applicable limit must be respected.

A default speed limit applies automatically to a particular road type or area when no traffic sign indicates another limit. Examples include general limits for motorways, built-up areas or roads outside built-up areas.

Usually, yes. A legally placed speed-limit sign normally introduces another maximum speed, although lower vehicle-specific or special-road limits may continue to apply.

A speed restriction normally begins at the location of the sign. Drivers should reduce their speed before passing the sign so that they are already travelling within the limit when it takes effect.

A signed limit may end at an intersection, an end-of-limit sign, another speed-limit sign or the beginning or end of a legally defined area. The exact rule differs between countries.

This depends on local law. An ordinary speed restriction may end at an intersection in some countries, while a zonal speed limit normally continues across intersections until an end-of-zone sign.

A speed zone is an area in which the displayed maximum speed applies throughout all included roads. The limit normally remains in force until the corresponding end-of-zone sign.

A variable speed limit is displayed on an electronic or changeable sign and may be adjusted according to congestion, weather, incidents or roadworks. When activated, it has the same legal importance as another applicable regulatory speed sign.

Yes. Signs positioned above individual lanes may impose different limits on those lanes. Drivers must observe the limit applying to the lane they use.

Yes. Temporary limits may be introduced near roadworks, collisions, hazards or special events. Drivers must follow the temporary traffic signs and instructions that are legally in force.

No. Overtaking does not normally permit a driver to exceed the applicable maximum speed. The manoeuvre must be completed safely while respecting the speed limit.

Some countries impose specific lower limits in rain, snow or other conditions. Even where the numerical limit does not change, drivers must reduce their speed sufficiently for the conditions.