Safe Driving Speeds, Curves, Braking, and Winter/Ice Conditions
What this domain tests
This section covers safe driving speeds, curves, braking, and winter or ice conditions for tank vehicles. The exam tests speed selection and control: the correct action is to reduce speed before the hazard, not correct during it.
Core rules
- Tank vehicles need lower speeds than cars on curves, ramps, and lane changes because of high center of gravity and surge.
- Slow down before a curve; a smooth, steady steering input is safer than braking while leaning.
- Increase following distance and brake gently and early; hard braking invites forward surge and wheel lock.
- On ice or snow, avoid cruise control, sudden throttle, and hard braking; use lower gears and gentle inputs.
- Bridges, overpasses, and shaded areas freeze first; reduce speed before reaching them.
Worked example
A tanker enters a downhill curve at the posted 45 mph. The road looks wet, and the trailer begins to lean. The driver brakes hard. Reasoning: braking in a curve adds longitudinal force while the tires are already working laterally, and forward surge can unload the rear axle. The correct approach is to select a lower gear before the downgrade, slow below 45 before the curve, and use light, steady braking. Once the vehicle is leaning, the driver should not add a hard brake input.
Traps
- Treating the posted car speed as safe for a tanker.
- Braking late and hard instead of slowing early.
- Using cruise control on slippery roads.
- Assuming wet roads are not icy because the temperature is above freezing.