Which of the following situations may cause inaccuracies in speed measurements?

When assessing speed measurement accuracy, variations in the speed of the patrol car while measuring can introduce significant errors. If the patrol car is accelerating, decelerating, or moving at an inconsistent speed during the measurement process, the radar unit's calculations may reflect an inaccurate speed reading.

Radar units calculate the speed of an object by analyzing the frequency change in the radar waves reflected off the vehicle being measured. If the source of the radar (the patrol car) is not maintaining a stable speed, it can affect the Doppler shift that is key to calculating the speed of the target vehicle. Thus, any fluctuations in the patrol car's speed can lead to unreliable readings, making this situation particularly problematic for accurate speed enforcement.

In contrast, the other situations, such as moving vehicles at a constant speed or stationary vehicles in a parking lot, are likely to produce more accurate readings because they either maintain a steady speed or do not factor into the speed measurement at all. Similarly, the fixed positions of the radar unit help to ensure that it consistently measures the target vehicle's speed without the added variable of the patrol car's movement impacting the measurement process.