During service brake testing, the inspector should stop the vehicle from what speed?

The correct answer is based on the requirement that during service brake testing, the vehicle should typically be stopped from a speed of 20 mph. This speed is significant as it provides a reliable measure of the effectiveness of the braking system under controlled conditions. Testing from this speed allows inspectors to assess how well the vehicle's brakes can bring it to a stop, which reflects more realistic situations that drivers might encounter on the road. Additionally, stopping from this moderate speed helps in evaluating the braking performance without introducing high-speed dynamics that could complicate the assessment.

It's essential because a 20 mph speed provides a balance between safety and the ability to observe brake function adequately. Lower speeds may not reveal potential issues that could manifest at higher operational speeds, while higher speeds could pose risks during the testing process. Thus, stopping from 20 mph is a standard protocol for assessing braking systems during inspections effectively.