North Carolina RADAR State Practice Exam

If an incorrect mode is used on a same direction moving RADAR, what is the expected behavior of the target speed display?

1. The display remains constant regardless of vehicle speed

2. The display changes by 1 mph for each change in patrol speed

3. The display changes by 2 mph in the opposite direction of the patrol speed

4. The display changes by 2 mph up or down for each mph change in patrol speed

The correct answer is: The display changes by 2 mph up or down for each mph change in patrol speed

When an incorrect mode is applied to a same-direction moving RADAR, the target speed display will reflect an inaccurate measurement of the vehicle's speed. In this case, it will change by an amount that deviates from the actual speed of the target vehicle based on the patrol speed. The reason the display changes by 2 mph up or down for each 1 mph change in patrol speed is tied to how the device interprets the relationship between the patrol and target speeds under the incorrect mode. For instance, if the patrol vehicle speeds up or slows down, the RADAR incorrectly calculates the target vehicle's speed as if it were moving in the opposite direction or compensating for the patrol speed incorrectly. This results in a doubling effect, where every 1 mph adjustment in patrol speed results in a 2 mph change in the displayed target speed. This behavior is critical for users of RADAR systems to understand, particularly in terms of ensuring accurate enforcement of vehicle speed laws. If one were to misunderstand this principle, it could lead to improper ticketing or legal issues due to inaccurate speed readings. It also underscores the importance of using the correct RADAR mode suited for the operational conditions.