Are Speed Traps Legal? State-by-State Map (2025)

What Is a Speed Trap?

Speed traps can take many forms, including both non-automated and automated.

Non-Automated Speed Traps

The phrase “speed trap” has existed for a long time. It could refer to any location where a police officer waits near a road to measure drivers’ speeds and stop speeders. Thus, the state trooper sitting in the trees with a radar gun could broadly be described as operating a speed trap.

But there are also a few more nuanced definitions for speed traps. In the days before radar guns, officers would use distance markers to estimate a driver’s speed based on the time required to span them. This process was notoriously inaccurate since fractions of a second could throw off the calculation.

Speed traps also refer to a law enforcement tactic that unfairly “traps” speeders, such as:

• Enforcing speeding laws at the base of a hill
• Setting up enforcement zones where speed limits drop without warning
• Hiding speed limit signs near trees or billboards

Often, small cities use these types of speed traps to supplement their revenue. Anecdotal evidence suggests that some towns with only a few hundred residents issue millions of dollars of tickets to people passing through using these strategies.

Generally, these types of speed traps are legal. However, California law prohibits old-fashioned speed traps where the speed limit suddenly drops without justification or the police use the inaccurate process of measuring speed by timing the distance traveled.

Since radar guns are nearly universally issued by police forces, measuring speed manually is almost obsolete. Speed traps involving drops in the speed limit are still occasionally used in small towns straddling highways, though. California law allows enforcement in these areas if a state survey has shown that the lower speed limit is justified. It only prohibits cities from lowering speed limits without proving the need for it.

Automated Speed Enforcement

Current usage refers to “speed traps” as locations with automated speed enforcement systems. These systems use built-in radar guns and cameras to perform the following:

• Measure the vehicle’s speed
• Capture a photograph of the vehicle’s license plate
• Store or transmit the information to a server to issue a ticket to speeders

These systems usually operate without supervision. In other words, most states that use automated speed enforcement do not require a human to review the system’s citations before mailing them to alleged speeders.

States usually set a margin to allow for speedometer inaccuracies. For example, many automated systems only deem a driver to be “speeding” when their speed is five or ten miles per hour over the limit.

Studies prove that automatic speed enforcement reduces speeding if drivers know where the systems are set up. In other words, fixed systems allow drivers to moderate their driving behaviors to avoid receiving an automatic ticket. This makes these systems especially useful in locations where a state has a special interest in preventing speeding accidents, such as work zones and school zones.

Moreover, some states limit where or how automated speed systems operate. For instance, Iowa allows speed cameras but limits their use as follows:

• Cities must obtain a permit to operate an automated speed enforcement system
• Only cities with over 20,000 residents can apply for a state permit
• The system only issues citations to drivers speeding by over 10 miles per hour

These types of limits try to balance the needs of police agencies to use the tools necessary to reduce speed-related auto accidents with the fair use of those tools.

How Speed Traps Work

Speed traps rely on radars, sensors and cameras to detect speeding vehicles. Radar cameras work by emitting radio waves and leveraging the Doppler effect. They measure the variation in frequencies when these waves bounce off a moving vehicle.

Using this information, the device calculates the vehicle’s speed. If it’s going too fast, then the machine takes a picture to issue a ticket.

There are also average speed cameras. This system involves placing two cameras at a certain distance from each other. The cameras record the license plate of each vehicle and the exact time at which it passed. By looking at the distance the vehicle traveled and how long it took the car to pass the second camera, the system can determine the average speed.

Mobile speed traps are similar to fixed radar units, but are placed on vans or other moving vehicles. They rely on radio waves and the Doppler effect, too.

Another type of speed trap is the sensor and camera system. These involve forward-facing cameras and lines painted on the road to measure the speed. This system functions by rapidly taking many pictures to get an idea of the distance the vehicle covers during a set amount of time.

Where Is Speed Trapping Illegal?

So are speed traps legal in every state in some form? Each state determines the tactics its law enforcement agencies can use to catch speeders. Most states allow tactics considered “speed trapping,” even if the circumstances seem unfair to drivers.

This means the police can usually set up enforcement areas at the base of a hill. Speed traps on highways and other high-traffic areas may be allowed as well.

However, nine states prohibit the use of speed cameras. The following states have laws banning the use of speed cameras:

• Texas
• Virginia
• Wisconsin
• New Jersey
• Maine
• New Hampshire
• Mississippi
• South Carolina
• West Virginia

One state, Nevada, allows automated speed cameras but only when human law enforcement officers are present. Two states, Utah and Arkansas, only allow them in certain areas, like school zones, residential neighborhoods and railroad crossings.

How to Challenge a Speed Trap Ticket

When looking for how to fight a speeding ticket, one of the first things to remember is to hire an attorney. Even if the process seems simple, you’ll need assistance in proving that you obeyed all traffic laws and should not have received the ticket.

Your lawyer may suggest a number of strategies that can help, including questioning the accuracy of the speed trap. The device could have malfunctioned and registered your speed incorrectly.

Similarly, if there was any type of interference, the reading could be wrong. Your lawyer might also ask to see how often the machine is maintained and what kind of issues it may have previously had.

Another strategy could be to contest the identity of the vehicle shown on camera. If there were similar vehicles in the vicinity and the license plate number is not clear, then that could help clear the ticket.

Additionally, you can establish that you were speeding because of an emergency or because you or a loved one was in danger. Medical emergencies can necessitate speeding. You will need strong proof that shows what the emergency was for this defense to succeed.

Contact ConsumerShield to Learn More About Speed Traps

Speeding tickets, including automated citations, can affect your insurance rates or even result in a license suspension. How long does a speeding ticket stay on your record? It depends on the state. Thus, the best way to avoid the effects of an unfair ticket is to beat it in court.

The knowledgeable team at ConsumerShield helps people understand their legal rights and find a trusted local lawyer to defend them. Contact us for a free case review and an attorney referral today.