Radar speed signUnited States
Traffic rules
United States
37. Radar speed sign
A radar speed sign warns drivers that vehicle speeds may be monitored by a fixed camera, mobile radar, lidar or average-speed enforcement system. It reminds drivers to check and respect the applicable speed limit.
The sign does not normally establish the speed limit itself. Drivers must follow the general, posted or variable speed limit applying to the road and must not brake suddenly merely because speed enforcement is indicated.
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What does a radar speed sign mean?
It warns that vehicle speeds may be measured or enforced on the road ahead or throughout a specified section.
Is a radar speed sign the same as a speed-limit sign?
No. A speed-limit sign establishes the maximum legal speed. A radar sign only warns that compliance with an applicable limit may be monitored.
Where can the applicable speed limit be found?
Check the most recent speed-limit sign, variable sign, speed-zone sign or general limit applying to the road and vehicle category.
Does the radar sign impose a lower speed?
No. It does not normally change the existing limit. Drivers must nevertheless travel more slowly when traffic, visibility, weather or road conditions require it.
Does the sign mean a camera is definitely present?
It may announce a permanent camera, a mobile-control area or a section where enforcement can occur. The exact meaning depends on the country and sign design.
Does the sign guarantee that the camera is active?
No. Drivers should never rely on assumptions about whether equipment is operating and should respect the speed limit at all times.
What is a fixed speed camera?
A fixed speed camera is permanently installed at a particular location and measures the speed of passing vehicles.
What is a mobile speed camera?
A mobile speed camera is temporarily positioned in a police vehicle, trailer, roadside unit or another approved location.
What is lidar speed enforcement?
Lidar uses laser pulses to measure the speed and position of vehicles. It may be used by police officers or in temporary automatic installations.
What is average-speed enforcement?
Average-speed enforcement records a vehicle at two or more points and calculates its average speed across the controlled section.
Can slowing only at the camera avoid an average-speed offence?
No. Average-speed enforcement considers the travel time across the complete measured section rather than speed at only one point.
Can a camera enforce both speed and red lights?
Yes. Some systems monitor vehicle speed and whether a vehicle passes a red traffic signal.
Is a radar warning sign legally required everywhere?
No. Some authorities announce speed cameras, while others permit enforcement without advance warning. The rules differ between countries and regions.
Can speed enforcement occur without a radar sign?
Yes. The absence of a warning sign does not normally prevent police or authorised authorities from carrying out a lawful speed check.
Does the sign give permission to drive at the displayed road limit?
The applicable limit remains a maximum rather than a target. Drivers must reduce speed whenever travelling at that limit would be unsafe.
Should you brake suddenly after seeing the sign?
No. Check your speed and reduce it smoothly when necessary. Sudden braking can cause a rear-end collision.
May you accelerate again after passing the camera?
Only while remaining within the applicable limit and driving safely. The restriction may continue, and another camera or average-speed section may follow.
Does the radar sign end the speed limit?
No. Passing a camera or radar sign does not end the applicable speed restriction.
What is a radar speed display?
A radar speed display measures an approaching vehicle and shows its current speed, sometimes with a colour, message or smiley symbol.
Is a radar speed display an enforcement camera?
Not necessarily. Many displays are preventive devices intended to make drivers aware of their speed and may collect anonymous traffic statistics without issuing penalties.
Is the displayed speed legally authoritative?
No. The roadside display is generally informational. Drivers remain responsible for observing the vehicle’s speedometer and the legal speed limit.
Can radar monitor motorcycles?
Yes. The technical ability to measure a motorcycle and the method used to identify it depend on the enforcement equipment.
Can a camera monitor several lanes?
Yes. Modern systems may measure vehicles in one or more lanes and may distinguish between traffic directions or vehicle categories.
Can different vehicles have different speed limits?
Yes. Heavy vehicles, buses, trailers or other vehicle categories may be subject to lower limits than passenger cars on the same road.
What should you do when you are already exceeding the limit?
Release the accelerator and reduce speed smoothly and safely. Do not brake harshly or make an abrupt lane change.
