Section 8: Tank Vehicles

This section is for drivers who drive tank vehicles

This section has information needed to pass the CDL knowledge test for driving a tank vehicle. You should also study Sections 2, 5, and 6. A tank vehicle is used to carry any liquids or gaseous materials in tanks.

Before loading, unloading, or driving a tank vehicle, inspect the vehicle. Make sure that the vehicle is safe to carry the liquid or gaseous material and is safe to drive.

Tank Endorsement is needed.

Tank Vehicle Defined

A tank vehicle includes any commercial vehicle which has fixed tanks (including collapsible containers, also called "bladder bags") or that carry portable tanks of 1,000 gallons or more capacity (CVC §15210(k)). Portable tanks are bulk containers which are not permanently attached to a vehicle. The product is loaded or unloaded while the portable tanks are off the vehicle, they are then loaded on a vehicle for transportation.

A tank vehicle also includes any fixed tank in excess of 119 gallons mounted on any vehicle or vehicle combination which requires a CDL or placards. (Example, a pickup transporting a 120 gallon fixed tank containing diesel requires a commercial Class C with Tank/HazMat endorsements. However, no CDL is needed for a 25,999 GVWR 2-axle truck with a 3000 gallon water tank pulling a trailer less than 10,000 lbs. GVWR.)

Inspecting Tank Vehicles

Tank vehicles have special items that you need to check. Tank vehicles come in many types and sizes. You need to check the vehicle's operator's manual to make sure you know how to inspect your tank vehicle.

On all tank vehicles, the most important item to check for is leaks. Check under and around the vehicle for signs of any leaking. Don't carry liquids or gases in a leaking tank. In general, check the following:

  • The tank's body or shell for dents or leaks.
  • The intake, discharge, and cut-off valves. Make sure the valves are in the closed position except when loading or unloading.
  • The pipes, connections, and hoses for leaks especially around joints.
  • The manhole covers and vents. Make sure the covers have gaskets and they close correctly. Keep the vents clear so they work correctly.
Special Purpose Equipment

If your vehicle has any of the following equipment, make sure it works:

  • vapor recovery systems
  • grounding and bonding cables
  • emergency shut-off systems
  • built-in fire extinguisher and/or system

Make sure you know how to operate your special equipment.

  • Check the emergency equipment required for your vehicle. Find out what equipment you are required to carry and make sure you have it and it works.

Driving Tank Vehicles

Speeding in a Tank Vehicle

If you are driving a tank vehicle containing more than 500 gallons of flammable liquid, which is subject to CVC §34000, faster than the speed limit allowed, you are subject to a $500 fine for a first offense. Stiffer penalties apply for a second or subsequent offense.

Hours of Service in a Tank Vehicle

The maximum driving time within a work period is 10 hours for drivers of tank vehicles with a capacity greater than 500 gallons when transporting flammable liquid. (49 CFR 395.1)

Liquids in bulk are transported in tanks, mounted on trucks, semitrailers, or full trailers. Transporting liquids, including liquefied gases, in tanks requires special skills because of the high center of gravity and the liquid surge of the cargo. Transit mix trucks and cement mixers are considered tank vehicles for purposes of a California CDL.

High Center of Gravity

High center of gravity means that the load is carried high up off the road. This makes the vehicle top-heavy and easy to roll over. Tankers often roll over. Tests have shown that tankers can turn over even at the cautionary speeds posted for curves. You should drive on highway curves or onramp/ offramp curves well below the posted speeds.

Liquid Surge

Liquid surge results from movement of the liquid in partially filled tanks. For example, when coming to a stop, the liquid will surge back and forth. When the wave hits the end of the tank, it tends to push the truck in the direction the wave is moving. If the truck is on a slippery surface such as ice, the wave can shove a stopped truck into an intersection. The driver of a tanker must be very familiar with the handling of the vehicle.

Controlling Surge
  • Keep a steady pressure on the brakes.
  • To control the surge do not release brakes too soon when coming to a stop.
  • Brake far in advance of a stop and increase your following distance.
  • If you must make a quick stop to avoid a crash, use controlled or stab braking. Also, remember that if you steer quickly while braking, your vehicle may roll over.

Some liquid tanks are divided into several smaller tanks by bulkheads. Bulkheads are liquid-tight separators between compartments inside the tank. When loading and unloading the smaller tanks, the driver must pay special attention to weight distribution. Do not put too much weight on the front or rear of the vehicle.

Baffled Tanks

Some tanks have compartments in them that have holes. If the compartment walls have holes in them, they are called baffles. Baffles let the liquid flow through and help control the forward and backward liquid surge. However, side to side surge can still occur which can cause a rollover. Drive slowly and be careful in taking curves or making sharp turns with a partially or fully loaded tanker.

Unbaffled Tanks

Smooth bore (or unbaffled) tankers have nothing inside to slow down the flow of the liquid. Therefore, forward and back surge is very strong. Smooth bore tanks are usually those that transport food products such as milk. Sanitation regulations rule out the use of baffles because of the difficulty in cleaning the inside of the tank. Corrosive liquids are also routinely transported in smooth bore tanks. Be extremely cautious (slow and careful) when driving smooth bore tanks, especially when starting and stopping.


Never load a cargo tank totally full. Liquids expand as they warm and you must leave room for the expanding liquid. This is called outage. Since different liquids expand by different amounts, they require different amounts of outage. You must know the outage requirement of your load when transporting liquids in bulk.

How Much to Load?

A full tank of dense liquid such as some acids may exceed legal weight limits. For that reason, you may often only partially fill tanks with heavy liquids. The amount of liquid to load into a tank depends on:

  • The amount the liquid will expand in transit.
  • The weight of the liquid.
  • Legal weight limits.
  • Temperature of the load.

Safe Driving Rules

In order to drive tank vehicles safely, you must remember to follow all the safe driving rules. A few of these rules are:

  • Drive smoothly. Because of the high center of gravity and the surge of the liquid, you must start, slow, and stop very smoothly. Also, make smooth turns and lane changes.
  • If you must make a quick stop to avoid a collision, use controlled or stab braking. (See Section 2.) Remember that if you steer quickly while braking, your vehicle may roll over.
  • Slow down before curves and accelerate slightly when coming out of the curve. The posted and/or advisory speed for a curve may be too fast for a tank vehicle.
  • Keep in mind how much space you need to stop your vehicle. Remember that wet roads double the normal stopping distance. Empty tank vehicles may take longer to stop than full ones.
  • Don't over steer, over accelerate, or over brake. If you do, your vehicle may skid. On tank trailers, if your drive wheels or trailer wheels begin to skid your vehicle may jackknife. When any vehicle starts to skid, you must take action to restore traction to the wheels.

Section 7: Doubles and Triples | Table of Contents | Section 9: Hazardous Materials/Wastes