The CDL Tank Vehicles endorsement (N endorsement) is required when you drive vehicles with liquid or gaseous cargo tanks of 1,000 gallons or more. Tank driving jobs are in high demand and typically pay well above average CDL rates.
When Is the N Endorsement Required?
You need a Tanker endorsement when:
- The tank is permanently attached to the vehicle or chassis
- The tank capacity is 1,000 gallons or more
- The tank is designed to transport liquid or gaseous material
Examples: fuel tankers, milk tankers, chemical tankers, compressed gas tankers, water tankers.
The X Endorsement: HazMat + Tanker
If you transport hazardous liquid or gas in a tank, you need both the H (HazMat) and N (Tanker) endorsements. Many states issue an "X" endorsement as a combined H+N designation for drivers who hold both.
Test Format
- Questions: ~20–30 questions (varies by state)
- Passing score: 80%
Key Test Topics
Liquid Surge
Liquid surge (also called surge or slosh) is one of the biggest hazards when driving a tank. As you brake or turn, liquid in a partially filled tank shifts forward, backward, or sideways — pushing the vehicle in the direction of the surge. Key points:
- Liquid surge is worse with partially filled (unbaffled) tanks
- Baffles reduce forward and backward surge but not side-to-side
- Smooth acceleration and braking reduce surge risk
High Center of Gravity
Tank vehicles have a higher center of gravity than most trucks, making them more prone to rollover. Slow down before curves and on ramps — more than the posted speed limit suggests.
Outage
Outage refers to the space left unfilled in a liquid tank to allow for liquid expansion. Some liquids expand significantly when heated. Drivers must understand the outage requirements for the specific cargo they're carrying.
Cargo Compatibility
Tankers must be inspected and cleaned between loads to prevent contamination — especially when switching between different types of cargo. Some materials are incompatible and cannot share a tanker without thorough cleaning.
Leaks and Emergency Procedures
Know how to check for tank leaks before and during a trip, and what to do if a leak occurs (pull off safely, notify emergency services, do not attempt to plug leaks in pressurized tanks without training).
Tank Driving Jobs
- Petroleum tanker driver: $65,000–$95,000/year
- Chemical tanker driver: $60,000–$90,000/year
- Milk/food-grade tanker: $55,000–$75,000/year
- Compressed gas tanker: $70,000–$100,000+/year
Study Tips
- Focus heavily on liquid surge — it's the most-tested topic on the Tank Vehicles exam
- Understand the difference between baffled and unbaffled tanks
- Review the outage rules — percentages vary by cargo type
- Practice with Tank Vehicle-specific questions before your exam