Combination #2
Combination Vehicles Practice Test | Texas 2026 #2 Page 3 of 3
Train for FREE online with our Texas CDL combination vehicle test. The official exam test consists of several obligatory parts, with all of them checking your knowledge of different blocks of road rules. If you need to obtain a TX combination license in 2026, practice as much as possible. Free sample tests published on our website will help you check and improve your knowledge and boost your grades. Please bear in mind that DMV requirements for issuing a combination license may vary from state to state.
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15 . During a trip, which shut-off valves should be open?
No shut-off valves should be open.
When starting a trip, be sure that all shut-off valves are in the open position, except for the last valves on the rear trailer. It is important that air reaches the brakes on all trailers and that the air is not able to escape from the back of the vehicle.
16 . A combination vehicle has:
Four air lines.
Combination vehicles have two air lines: a service line and an emergency line.
17 . The service air line is attached to the:
Steering wheel.
The service air line carries air and is controlled by either the foot brake or trailer hand brake. The service air line is attached to relay valves, which allow the trailer brakes to be applied quickly.
18 . To test the trailer service brakes, you should:
Move the vehicle forward slowly and apply the brakes with the hand control.
To test the trailer service brakes, you should first ensure that the braking system has a normal air pressure level, then release the parking brake. You should then move the vehicle forward slowly and apply the brakes with the hand control. If the trailer service brakes are working properly, you will feel the brakes activate.
19 . To prevent a rollover, a driver should:
Turn quickly.
Rollovers can happen when a combination vehicle is turned too quickly. To help prevent the risk of rollover, it is important to keep the vehicle's center of gravity low by loading cargo as close to the ground as possible.
20 . One function of the emergency air line is to:
Control the ability to maneuver during bad weather conditions.
