How old must you be to drive a commercial vehicle across state lines?
At 18 you can usually drive only within your state (intrastate).
What CDL class do you need for a combination with a gross weight over 26,000 lb when the towed unit is over 10,000 lb?
Class B covers heavy single vehicles; Class C covers smaller vehicles carrying passengers or hazmat.
Which endorsement letter is for hazardous materials?
N is tanker, T doubles/triples, P passenger.
What is the blood alcohol limit for a driver of a commercial motor vehicle?
It is half the limit for car drivers in most states.
Under federal hours-of-service rules, how many hours may a property-carrying driver drive after 10 hours off duty?
Driving must also end by the 14th hour after coming on duty.
When must a property-carrying driver take a 30-minute break?
The break is required after 8 cumulative hours of driving without a 30-minute interruption.
How far ahead should you look while driving a truck?
At highway speed that is about a quarter mile.
You drive a 40-foot vehicle at over 40 mph. How many seconds should you leave behind the vehicle ahead?
One second for each 10 feet of length (4), plus one second above 40 mph.
What causes most serious skids?
Over-braking, over-steering and over-accelerating are the usual triggers, mostly from going too fast.
At what speed can hydroplaning start if there is a lot of water on the road?
Lower speed and good tread reduce the risk.
What is the minimum tread depth for the front (steering) tires?
Other tires need at least 2/32 inch.
You stop on a two-lane road. Where do you place your warning triangles?
Place them within 10 minutes of stopping.
Before the air pressure in the tanks drops below what level must the low-pressure warning come on?
If the warning comes on, stop safely as soon as possible.
At what tank pressure do spring brakes usually come on by themselves?
This is why low air pressure is an emergency.
Why do you do a pre-trip inspection?
Federal and state law also require it.
What does this sign warn truck drivers about?
Choose your gear before the grade; let the engine hold your speed and use the brakes as backup.
A vehicle shows this placard. What does it carry?
Placards are diamond-shaped, at least 250 mm on each side, and are shown on all four sides of the vehicle.
This marking is painted on your lane. What does it mean?
Some vehicles, including buses and many hazmat loads, must stop at every railroad crossing.
Which vehicles must stop at every railroad crossing, even with no train in sight?
Stop 15 to 50 feet from the nearest rail, look and listen, and do not shift gears while crossing.
Answer key
About this test
- To get a Class A or B CDL you pass written knowledge tests at your state DMV, starting with General Knowledge (usually 50 questions, 80% to pass), then a skills test.
- Most trucks also need the Air Brakes test; endorsements such as Hazmat (H), Tanker (N) and Doubles/Triples (T) have their own tests.
- State CDL manuals follow the same federal model, so the rules here apply nationally. These are our own practice questions.
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