How does the FMVSS require that the vehicle be positioned for checking parking brake operation?

The correct approach for checking parking brake operation, according to FMVSS (Federal Motor Vehicle Safety Standards), is to position the vehicle on a slope of a specified degree. This requirement is essential to simulate conditions under which a parking brake must effectively hold a vehicle in place, ensuring that the brake's performance can be accurately assessed.

Positioning on a slope tests the effectiveness of the parking brake by applying gravitational force that the brake system must counteract. A 30-degree slope is typically specified within the regulations to ensure a stringent evaluation of the parking brake's holding capability. This scenario reflects a real-world situation where a vehicle needs to remain stationary on an incline, making it crucial for safety assessments and compliance with safety standards.

Other positioning options, such as on flat surfaces or parallel to a curb, do not provide the required testing conditions necessary to accurately evaluate the functionality of the parking brake. Similarly, a 15-degree slope may not be sufficient to accurately test the efficiency of the brake in more extreme conditions. Thus, the use of a 30-degree slope is directly aligned with ensuring the parking brake meets the safety requirements laid out by FMVSS.