Because of liquid surge and a high center of gravity, tank vehicle drivers should be especially cautious about
- Using turn signals before changing lanes
- Checking mirrors before backing up
- Keeping the fuel tank more than half full
- Sudden steering or braking maneuvers, such as swerving to avoid an obstacle, which can trigger a rollover (correct)
A quick swerve can send the surging liquid sharply to one side just as the truck's high center of gravity is already unsteady. That combination is a leading cause of tank vehicle rollovers, so drivers are trained to steer and brake smoothly and plan further ahead than they would in a dry van.
Source: 49 CFR 383.119.
Why are cargo tanks generally not filled to 100 percent of their capacity?
- Federal law requires tanks to run partly empty specifically to reduce insurance costs
- A completely full tank leaves no room for the liquid to expand as it warms, which can cause overflow or excess pressure (correct)
- It has no real safety purpose, only a business one
- Full tanks are always too heavy to legally register
Liquid volume rises with temperature, and a tank filled to the brim would build pressure or force product out as the load warms during the trip. Federal filling rules set outage requirements for that reason, which is why shippers stop short of the top rather than as a matter of preference.
Source: 49 CFR Part 173.
According to federal knowledge requirements for the tank vehicle endorsement, a driver must understand that a tank vehicle's handling changes depending on
- The color of the tractor
- The brand of tires mounted on the trailer
- Whether the tank is full, partially full, or empty, since each state changes how the liquid load moves and affects braking, acceleration, and steering (correct)
- Whether the driver has more than five years of experience
A full tank, a partly filled tank, and an empty tank each behave differently because the amount of liquid free to move changes. The federal knowledge requirements for the tank endorsement specifically call for understanding how that changes braking, acceleration, and steering.
Source: 49 CFR 383.119.
