North Carolina RADAR State Practice Exam

Which of the following conditions will Same Direction Moving RADAR not compute?

1. Speeds that differ by more than 12 mph

2. Speeds closer than 3-6 mph from patrol vehicle speed

3. Speeds where the target vehicle is stationary

4. Speeds that exceed patrol vehicle speed

The correct answer is: Speeds closer than 3-6 mph from patrol vehicle speed

Same Direction Moving RADAR technology has specific limitations when measuring the speed of target vehicles. The correct response highlights that this system will not compute speeds that are closer than 3-6 mph from the patrol vehicle speed because of the fundamental principle of Doppler radar. In the context of Same Direction Moving RADAR, it requires sufficient disparity between the speeds of the patrol vehicle and the target vehicle to accurately calculate the target's speed. When the target vehicle’s speed is too close (within that 3-6 mph range) to the patrol vehicle’s speed, the radar may not be able to distinguish between the two moving objects effectively. This can lead to erroneous or unreliable speed readings due to the way the Doppler effect works, as the radar reflections from the target vehicle blend too closely with the radar signals from the patrol car, making a clear computation impossible. In contrast, the other options entail scenarios that are outside this specific limitation. For instance, the system can compute speeds that differ by more than 12 mph, that involve stationary targets, or speeds that exceed the patrol vehicle's speed, as these conditions create a clear distinction necessary for the radar to function correctly.