Code L (restriction removal)
Compatible with: Class A, Class B
Air Brakes (Restriction Removal)
Remove the restriction. Drive any commercial vehicle.
Difficulty
Moderate
Salary Impact
Required for all standard CDL positions — not optional
TSA Required
No
What Is the Air Brakes Endorsement?
Air brakes is not technically an endorsement — it is a restriction removal. If you take your CDL skills test in a vehicle without air brakes, a code L restriction is placed on your license, prohibiting you from operating vehicles with air brakes. Passing the Air Brakes knowledge test and skills test in an air-brake-equipped vehicle removes this restriction. Nearly all commercial vehicles use air brakes, making this removal essential.
Who Needs This Endorsement?
Every CDL holder who wants to operate commercial vehicles — which is virtually all of them. The L restriction severely limits your employability. Buses, semi-trucks, dump trucks, tankers, and most commercial vehicles use air brakes. Removing this restriction is not optional for a working CDL career.
How to Obtain It
- 1Pass the Air Brakes knowledge test at DPS (25 questions; 80% passing score)
- 2Take your CDL skills test in a vehicle equipped with air brakes
- 3No additional background check required
- 4One-time process — once removed, no renewal needed
Knowledge Test Topics
Study Tips
- Draw and label the air brake system components — this helps memorization
- Memorize the pre-trip air brake inspection sequence (two-step test)
- Understand the difference between service brakes, parking brakes, and spring brakes
- Study the low air pressure warning threshold (60 PSI) and spring brake activation (20–45 PSI)
- Review brake fade causes and prevention on long downgrades
Career Impact
Removing the air brake restriction is essential for virtually every CDL career path. Without it, you cannot legally drive semi-trucks, buses, tankers, dump trucks, or most commercial vehicles. It is the single most important step after obtaining your CDL.
How Diesel Xtrem Prepares You
All Diesel Xtrem training vehicles are equipped with air brakes. You take your skills test in our vehicle, which automatically removes the L restriction from your CDL. We cover the Air Brakes knowledge test material in detail so you pass on the first attempt.