CDL Rules Drivers Are Tested On
Hours of service, alcohol, phones, rail crossings, warning triangles, the medical card and what costs you your CDL, each with the section it comes from.
How many hours can I drive?
Truck drivers start each shift after 10 hours off duty. Then they may drive up to 11 hours, and not after the 14th hour on duty. After 8 hours of driving they need a 30-minute break.
Bus drivers may drive up to 10 hours after 8 hours off duty, and not after 15 hours on duty.
| Limit | Trucks | Buses |
|---|---|---|
| Off duty before driving | 10 hours | 8 hours |
| Driving | 11 hours | 10 hours |
| On duty, then no more driving | 14 hours | 15 hours |
| Weekly | 60 hours in 7 days, or 70 in 8 | 60 hours in 7 days, or 70 in 8 |
49 CFR 395.3 and 395.5. Trucks can restart the weekly count after 34 hours off (395.3(c)).
What are the alcohol rules?
No alcohol within 4 hours before going on duty, and none at all on duty. An alcohol concentration of 0.04 or more while driving a commercial vehicle costs you your CDL for a year, or 3 years if you were carrying placarded hazmat.
Refusing a test counts the same as failing one. A second offense means losing your CDL for life.
49 CFR 392.5(a) and 383.51(b), Table 1.
Can I use my phone while driving?
Not in your hand. Texting and holding a phone are banned while driving, including while stopped in traffic, except to call the police or emergency services. Two convictions in 3 years cost you your CDL for 60 days.
49 CFR 392.80, 392.82 and 383.51(c), Table 2.
When must I stop at a railroad crossing?
Buses carrying passengers, and vehicles carrying chlorine or placarded with certain hazmat, must stop 15 to 50 feet before the tracks, then look and listen both ways before crossing.
Every other commercial vehicle must approach slowly enough to stop before the tracks. Breaking a crossing rule costs your CDL for at least 60 days.
49 CFR 392.10, 392.11 and 383.51(d), Table 3.
Where do the warning triangles go?
Turn on your hazard flashers at once. Within 10 minutes, put out three triangles: 10 feet behind your vehicle on the traffic side, 100 feet behind it, and 100 feet ahead of it. On a divided or one-way road, put them 10, 100 and 200 feet behind.
49 CFR 392.22.
How often do I need a medical exam?
At least every 24 months, or every 12 months with insulin-treated diabetes or under the vision standard’s alternative.
49 CFR 391.45.
Do I have to wear a seat belt?
Yes, whenever the seat has one, and in a truck so must anyone riding with you.
49 CFR 392.16.
What else costs me my CDL?
Driving under the influence, leaving the scene of an accident or using the vehicle in a felony: a year for a first offense, 3 years with hazmat, and life for a second. Serious traffic violations such as speeding 15 mph over or following too closely: 60 days for a second in 3 years, 120 days for a third.
49 CFR 383.51(b) and (c), Tables 1 and 2.
Practice These Rules
The general knowledge test asks about all of them, in the real test’s format. General Knowledge Test · Hazmat Test
Every rule here is from Title 49 of the Code of Federal Regulations as it stood on November 1, 2026. Your state can add its own rules.