Liquid Surge, Slosh, and Vehicle Handling
What this domain tests
This section covers liquid surge, slosh, and vehicle handling. The exam tests whether you understand that liquid movement in a partly filled tank is not just a comfort issue: it can push a vehicle through a stop, upset steering, or cause a rollover.
Core rules
- Surge is worst in a smooth-bore tank with a partial load, because the liquid has a long free surface and nothing to slow it.
- Baffles reduce the distance and speed of liquid movement but do not eliminate surge.
- Forward surge occurs when you brake; rearward surge occurs when you accelerate; side surge occurs in curves and lane changes.
- Start, stop, and steer smoothly. Leave extra stopping distance and avoid sudden lane changes.
- If surge begins, do not overcorrect; reduce speed smoothly and keep steering inputs small.
Worked example
A smooth-bore tanker with a half load approaches a red light. The driver brakes firmly at the last moment. The liquid surges forward, adding force to the front axle and reducing traction on the rear; the trailer may push the tractor. Reasoning: the driver needed to brake earlier and gentler, using a longer following distance. After stopping, the liquid can surge rearward and then forward again, so the driver should hold the brake and wait for movement to settle before accelerating.
Traps
- Thinking baffles make a tank surge-proof.
- Assuming a partial load is safer because it is lighter.
- Accelerating hard to pull out of a surge.
- Following too closely, which forces late, hard braking.