# Free Delaware CDL Combination Vehicles Practice Test 2023

Our CDL practice tests:
Based on 2021 DE commercial driver's license manual
Perfect for first-time, renewal applicants
DE CDL Combination Vehicles Test format:
20 questions
80% passing score
List of questions
1.
When a vehicle goes around a corner, the rear wheels follow a different path than the front. This is called:
2.
The air lines on a combination vehicle are often colored to prevent them from mixing up. The emergency line is _____, the service line is _________.
3.
The trailer air supply control knob is _____.
4.
Spring brakes are not required on trailers and dollies built before:
5.
To prevent water and dirt from entering the air system, hose couplers can be attached to dummy couplers or:
6.
When connecting the glad hands, press the two seals with the couplers together at what degree to each other?
7.
Tractor with a ______ trailer requires the shortest amount of stopping distance.
8.
When driving a combination vehicle with multiple trailers or dollies, all air shut-off valves except the last one at the back must be:
9.
A major leak in the trailer emergency line will cause:
10.
When parking trailers without spring brakes, it is very important to:
11.
The emergency air line is usually what color?
12.
Trailer landing gear ________.
13.
Why should you be sure that the fifth wheel plate is greased as required?
14.
In normal driving, some drivers use the hand valve before the brake pedal to prevent a jack-knife. Which of the statements is true?
15.
The "rearward amplification" value means _______.
16.
Rocky mountain doubles have a rearward amplification of about:
17.
After connecting the air lines but before backing under the trailer you should:
18.
If you cannot complete your turn without entering another traffic lane you should:
19.
In case of landing gear failure while pulling out from under it, you should:
20.
Why should you lock the tractor glad hands to each other (or dummy couplers) when you are not towing a trailer?