CDL Vehicle Combination Practice Test

The first step when coupling a trailer should focus on the alignment of the tractor and trailer. Proper alignment ensures that the fifth wheel can properly engage with the kingpin of the trailer. Once the tractor is aligned with the trailer, coupling can proceed safely and effectively. While connecting the air supply lines is vital for operating the trailer's brakes and other systems, it should occur after the tractor and trailer are securely coupled. Inspecting the coupling mechanism is also a necessary step, but it comes after ensuring the initial alignment. Securing the trailer brakes is important for safety, but it does not take precedence over the correct positioning of the units for proper connection. Thus, proper alignment is the essential first step in the coupling process.