Speed limit

A legally established maximum or minimum speed for vehicles on a road or within an area. Limits may vary by vehicle type, conditions, and time.

Posted speed limit: A speed limit displayed on a roadside sign or electronic traffic sign. Signs communicate the legally applicable limit at a particular location.
Road safety: The prevention of traffic collisions and reduction of their harmful consequences. Speed limits are used to reduce both collision likelihood and impact severity.
Vehicle speed: The rate at which a vehicle changes position over time. A speed limit places a legal ceiling or floor on this measurable quantity.
Advisory speed: A recommended speed for a road feature or condition, usually not a statutory maximum. Advisory speeds warn about hazards without necessarily setting a legal limit.
Traffic collision: An event in which a road vehicle strikes another vehicle, person, animal, or object. Speed influences both the chance of a collision and its consequences.
Speed-limit sign: A traffic sign that displays a legal speed limit or advises a speed for a road section. Its design and placement make the limit visible to drivers.
Traffic calming: Road design and traffic measures intended to reduce vehicle speeds and improve conditions for other users. Physical design can reinforce a posted limit where signs alone are insufficient.
Stopping distance: The distance a vehicle travels from the moment a driver detects a hazard until it stops. Higher speed generally lengthens the distance needed to avoid a hazard.
Basic speed law: A legal rule requiring drivers to travel at a speed reasonable for current conditions. It can prohibit unsafe speed even when a driver remains below the posted limit.
Road traffic injury: Physical harm resulting from a collision or other incident involving road traffic. Lower impact speeds can reduce the severity of injuries.

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