Minnesota CDL: Tanker Vehicles Practice Test

Not quite. The answer is Surge can move the truck in the direction the liquid waves move.

One of the reasons you must drive a tanker vehicle carefully is that liquid surge can push the vehicle in the same direction as the surge. This can be especially hazardous on icy roads, where a truck may be pushed forward a dangerous amount, maybe past a red light into an intersection.

Not quite. The answer is baffles.

Baffles are devices that regulate the flow of liquid. In a tank vehicle, baffles are a type of bulkhead with holes through which liquid may flow but with reduced force.

Not quite. The answer is MC-306 (DOT-406)

MC-306 (DOT-406) cargo tanks carry liquids under very low or no pressure (maximum allowable pressure of 3 psi for MC-306 and 4 psi for DOT-406). The cargo tank has an oval or elliptical cross section and is usually compartmented. These tanks are commonly used to carry gasoline, diesel fuel or fuel oil, and other flammable liquids.

Not quite. The answer is may require a longer stopping distance than full trucks.

With all types of combination vehicles, the weight of cargo helps the wheels get traction. When a combination vehicle is empty or lightly loaded, its braking distance increases. The very stiff suspension springs and strong brakes give poor traction and make it very easy to lock the wheels.

Not quite. The answer is 5 mph slower.

On a steep downgrade, don't keep applying your brakes continuously because this might cause them to fade (become less effective). Instead, apply your brakes sparingly as a supplement to engine braking. Select a "safe" speed. Let your vehicle reach this speed. Brake gently until you are going 5 mph slower. Then let your speed increase back to the "safe" speed. Keep varying your speed up and down this way. This technique is known as snub braking or snubbing.

Not quite. The answer is The posted speed for a curve may be too fast for a tank vehicle.

Tank vehicles have a high center of gravity. Much of a loaded tanker's weight is carried five or six feet above the ground. This makes a tanker top-heavy, which makes it more prone to rollovers than other types of vehicles. Tests have shown that a tank vehicle can roll over at the speed limits posted for curves. The safest way to take a curve in a tanker is to slow down well below the posted speed limit before you enter the curve.

Not quite. The answer is the distance you can see ahead.

No matter what type of motor vehicle you are driving at night (even a passenger car), you must drive at a speed that lets you stop within the range of your headlights. (In the dark, you have no way of knowing what lies beyond the reach of your headlights.) With low beams, you can see ahead only about 250 feet. Yet if you're driving a vehicle with air brakes at 45 mph, your vehicle's stopping distance may be as long as 346 feet. Hence, with low beams at 45 mph, you will not be able to brake in time to avoid a hazard that you see.

Not quite. The answer is 20 mph

If you've moved onto a shoulder that may have a loose surface, let your vehicle slow down to about 20 mph before you brake. Braking at a higher speed on a loose surface can cause a skid.

Not quite. The answer is both a hazardous materials (H) endorsement and a tank vehicle (N) endorsement.

A tank vehicle (N) endorsement qualifies you to haul liquids or gases. However, if those liquids or gases are classified as hazardous materials, you must also have a hazardous materials (H) endorsement to haul them. To obtain each of these endorsements, you must pass a specialized knowledge test. Note: These days, if you obtain both endorsements, your CDL may include the combined endorsement code X (tank vehicle and HazMat) instead of both H and N.

Not quite. The answer is both of the above.

When deciding how much liquid you can load on your tank vehicle, you must consider the weight of the liquid, the amount of space to allocate for the liquid to expand as it heats up (called outage), and all legal weight limits on your vehicle. A full tank of a dense liquid may exceed the legal weight limits, so you can only fill the tanks partially with such a liquid.

Not quite. The answer is There will be less front-to-back surge than in a tank without baffles.

A baffled tank has bulkheads with holes through which the liquid can flow forward or backward but with less force than if there were no baffles. This will reduce forward-and-backward surge, making it less likely that surge will push your vehicle forward when you try to stop.

Not quite. The answer is 1,000 gallons or more.

Federal regulations define a "tank vehicle" as a commercial motor vehicle designed to transport liquids or gases within tanks that have an individual rated capacity of more than 119 gallons each and an aggregate rated capacity of 1,000 gallons or more. To drive such tank vehicles, you must have a Tank (N) endorsement or Combination Hazmat and Tank (X) endorsement on your CDL.

Source: 49 CFR § 383.5

Not quite. The answer is on slippery roads.

When you're coming to a stop, the liquid in the tanks tends to surge forward. If you're on a slippery surface, the surge may shove your truck forward into another vehicle or an intersection. Learn how your tanker handles in such situations.

Not quite. The answer is the movement of the liquid.

It takes special skills to drive a tanker carrying liquid cargo because of the vehicle's high center of gravity and the possibility that the liquid cargo may surge forward and backward or from side to side. The liquid surge can push the vehicle dangerously forward or sideways, which can cause a rollover. Once a side-to-side surge begins, unless the driver takes action, the tank will keep swaying more and more until the vehicle rolls over.

Not quite. The answer is Much of the tanker's weight is high up off the ground.

An object with a high center of gravity is top-heavy; much of its weight is high off the ground. Top-heavy objects are more prone to toppling over. Loaded tankers tend to have a high center of gravity because the tanks are so tall. This makes liquid tankers more prone to rolling over. Tests have shown that tankers can roll over on curves even at the speeds posted. On curves, slow down well below the posted speeds.

Not quite. The answer is 70%

It takes special skills to operate a tank vehicle safely. About 70% of tank truck drivers haul hazardous materials, such as gasoline. Doing so takes even more special skills. Such drivers must obtain both a tank vehicle (N) endorsement and a hazardous materials (H) endorsement on their CDLs, or a combination tank vehicle and hazardous materials (X) endorsement.

Not quite. The answer is Slow down gradually.

Braking on a slippery surface can lock the wheels and cause a skid. Brake gently and slow down very gradually.

Not quite. The answer is with holes that let liquid flow through.

Tank baffles are bulkheads with holes through which the liquid can flow, but with less force than in tanks without such baffles. These baffles significantly reduce forward-and-backward surge but not side-to-side surge, so the risk of surge causing a rollover remains.

Not quite. The answer is If the wheels are skidding, you cannot control the vehicle.

In an emergency, avoid hard braking. Hard braking can lock the wheels, which may cause a skid and loss of control. Instead, use stab braking (unless your vehicle has antilock brakes) or controlled braking.

Not quite. The answer is side-to-side surge.

Some tanks have baffles: bulkheads with holes through which the liquid can flow forward or backward. These baffles significantly reduce forward-and-backward surge but not side-to-side surge, so the risk of surge causing a rollover remains.