What initial action is taken during a pre-trip inspection of brakes?

During a pre-trip inspection of brakes, checking air pressure gauges is a crucial initial action. This step is vital because the air pressure in the brake system must be within the manufacturer's specified range to ensure optimal braking performance. Adequate air pressure is essential for the proper functioning of the air brakes, as insufficient pressure can lead to brake failure and increase the risk of accidents.

Monitoring air pressure also allows the driver to identify potential issues with the braking system before driving, contributing to overall safety. This proactive approach helps drivers address any deficiencies that could lead to serious safety concerns while on the road. Other actions, such as checking warning lights or inspecting tire tread depth, are important for overall vehicle safety but do not directly address the specific functionality of the brakes in the same way that checking air pressure does.