Ohio CDL Practice Test 2025 - Complete Exam Preparation Guide

The primary function of a vehicle's air brake system is to provide safe stopping power for heavier vehicles. Air brakes are essential for large commercial vehicles, such as trucks and buses, which have a greater mass and require more robust braking systems to safely stop. Unlike traditional hydraulic brake systems, air brakes utilize compressed air, which allows for more effective braking performance, particularly under the significant weight of these vehicles.

The design of air brakes ensures that they can withstand the demands placed upon them due to the weight and size of heavy vehicles. This system includes safety features such as air reservoirs that maintain brake power even if the engine fails, enhancing overall safety.

Other options, while related to vehicle performance and function, do not capture the critical role of air brakes in stopping heavy vehicles. Fuel efficiency, engine cooling, and steering control, although important aspects of vehicle operation, are not the primary purpose of an air brake system. The focus on safe stopping power specifically aligns with the major concern of managing the stopping force needed to control larger vehicles, making it clear that the air brake system serves a vital function in ensuring road safety.