What is typically the fastest vehicle detected by a radar unit captured by the "lock" feature?

The choice of the fastest speed over a time frame as the correct answer reflects how radar units operate in capturing and processing speed data. When a radar unit is engaged, particularly when using the "lock" feature, it focuses on detecting and recording the speed of the vehicle traveling at the highest velocity within its field of view during a specified interval.

This feature is specifically designed to provide law enforcement officers with a reliable measurement of the highest speed observed within a set time frame, which is critical for identifying speeding violations. The radar unit locks onto the fastest target, thereby ensuring that the data presented for enforcement purposes is accurate and pertinent to the observed traffic situation.

In contrast, other options do not align with how the "lock" feature is utilized. For instance, averaging speeds of all vehicles or capturing speeds of the closest or furthest vehicle do not represent the primary function of the locking mechanism, which is to provide a definitive and immediate reading of the fastest individual vehicle detected. This capability is essential in speed enforcement scenarios, making the selected answer the most relevant in the context of radar operation.