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Yes. A police officer can measure your speed while traveling toward you, including with moving radar. The equipment accounts for the patrol car’s speed to calculate yours. Whether a specific ticket is valid depends on the method used, the evidence and the law where the stop occurred.
How moving radar measures an oncoming vehicle
Moving radar measures relative motion, or how quickly the distance between two vehicles is changing. With a front-facing antenna, the radar calculates the target vehicle’s speed by subtracting the patrol vehicle’s speed from the closing speed. The radar performs this calculation automatically and displays both the target speed and patrol speed, according to the National Highway Traffic Safety Administration’s 2018 radar operator-training manual.
The manual gives an illustrative example: a closing speed of 134 mph minus a patrol speed of 62 mph produces a target speed of 72 mph. That is a training calculation, not evidence about any particular traffic stop.
Radar aimed behind a moving patrol car
A rear-facing antenna can measure a vehicle moving away from the patrol car. In that configuration, the radar subtracts patrol speed from separation speed. The NHTSA manual’s example is 138 mph separation speed minus 64 mph patrol speed, producing a target speed of 74 mph. This, too, is an instructional example rather than a real ticket reading.
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Radar is not the only possible method
Do not assume radar was used just because the officer was driving. The Kansas Highway Patrol’s FAQ says its Doppler radar can measure vehicles traveling in either direction while the patrol unit is moving or stationary. It also describes lidar and time-distance methods as ways to measure speed. Check the citation or ask what method was used.
Does opposite-direction travel make a ticket invalid?
No—not by itself. The fact that the vehicles were traveling toward one another does not establish that a speed measurement was impossible or that a ticket must be dismissed. The method, the officer’s observations, device records, vehicle identification and local rules for using speed evidence may all matter.
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Those rules vary by jurisdiction. For example, Ohio Revised Code section 4511.091 addresses device-based speed enforcement and restricts convictions for specified speeding provisions based solely on unaided visual estimates. Virginia Code section 46.2-882 sets out requirements concerning speed-measuring devices. The Michigan State Police radar guidance describes radar configurations and references court guidelines for moving-radar evidence. These are examples of state-specific law and practice, not rules that apply everywhere or a determination of an individual ticket.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What to check if you received a ticket
- Read the citation. Note the alleged speed, location, cited statute and any information identifying the measurement method.
- Find the law and court procedure for that place. Use the current rules for the state or locality where the ticket was issued; another state’s requirements may differ.
- Identify what evidence exists. Depending on the case and local procedure, relevant details may include the officer’s observations, the device or method used, and available operator or device records.
- Get advice on the specific case if needed. A meaningful assessment requires the jurisdiction and citation details, as well as the method and any available records. No general answer can establish whether a particular reading is accurate or admissible.
A radar detector does not show whether an officer obtained an accurate or admissible reading. Nor does a GPS speedometer, which reports your own speed rather than the speed recorded for the targeted vehicle.
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