Inspecting a combination vehicle

Section 6.5 of the CDL handbook lists the extra checks for combination vehicles. It is tested on the Combination Vehicles test.

Key facts

Part of	the Combination Vehicles test (80% to pass)	DL-7C p. iv
Handbook section	§6.5 Inspecting a combination	DL-7C p. 6-12
Questions in CDL Mile's bank	10	CDL Mile, checked against DL-7C

Key rules

§ 6.5.1p. 6-13
The air-lines should be properly connected to the glad hands with no leaks. They should be secured but still have enough slack for turns, and be free of damage.
Additional Things to Check during a Walk-around Inspection
§ 6.5.2p. 6-13
Opening the emergency line valve at the back of the last trailer should release air. That shows air is reaching all the way back and the whole system is charged. Close the valve after the check.
Combination Vehicle Brake Check
§ 6.5.2p. 6-13
If no air comes out at the rear, check that the shut-off valves on the trailers and dollies are in the open position. Air has to reach the back for all the brakes to work.
Combination Vehicle Brake Check

Try two questions

Combination Vehicles · Inspecting a combination

Why does it matter that the tractor protection valve works correctly?

Tap an answer to see the explanation and the handbook page.

Combination Vehicles · Inspecting a combination

You charged the trailer air brakes and the trailer rolls freely. You stop and pull out the trailer air supply control. What do you do next to check the trailer emergency brakes?

Tap an answer to see the explanation and the handbook page.

Sources

Texas Commercial Motor Vehicle Drivers Handbook (DL-7C), revised March 2026, Texas Department of Public Safety. Page references are to its printed page numbers. CDL Mile is independent and not affiliated with Texas DPS.

Updated for the March 2026 Texas CDL handbook (DL-7C). Last checked November 4, 2026.

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