Question

Difficulty: Very hardWinter Driving, Snow, and Black Ice

While driving at night in sub-freezing temperatures (28F28^\circ\text{F}), a driver follows a commercial semi-truck across a shaded elevated overpass. The driver notices that the truck's rear tires suddenly stop producing water spray, even though the road surface ahead continues to look wet and dark. Which of the following describes the most accurate hazard assessment and correct defensive driving response?

  1. Recognize that the sudden absence of tire spray indicates the wet surface has frozen into black ice; maintain a steady steering wheel, gently ease off the accelerator without braking or sudden gear changes, and expand the following distance.Answer
  2. B
    Assume the road remains wet and safe to travel at the posted speed limit as long as visibility is clear and no snow accumulation is visible on the roadway.
  3. C
    Downshift quickly into a much lower manual gear to utilize aggressive engine braking before driving onto the bridge structure.
  4. D
    Apply firm, continuous pressure to the brake pedal immediately upon reaching the overpass to bring the vehicle to a stop on the shoulder until road crews apply salt.

Answer

The driver should recognize that the disappearance of tire spray on a dark road during freezing weather signals black ice formation, and respond by avoiding sudden braking or steering while smoothly easing off the accelerator to maintain traction.
The correct response identifies the sudden disappearance of water spray from tires on a dark road in sub-freezing temperatures as a definitive indicator of black ice. Elevated bridges freeze first because air flows around both sides of the structure. Smooth control adjustments—easing off the accelerator without braking, steering abruptly, or downshifting—preserve the small amount of tire traction available.

Step-by-Step Solution

1
Analyze visual cues for surface ice formation
Identify that a wet-looking road surface that produces no tire spray at temperatures below freezing (32F32^\circ\text{F}) indicates black ice.
Liquid water creates spray when tires pass over it; frozen ice forms a smooth coating that generates no spray.
2
Assess environmental vulnerability
Recognize that elevated structures such as overpasses freeze before normal road surfaces due to cold air circulating both above and below the bridge deck.
Elevated roadways lose heat rapidly from all exposed sides, accelerating ice formation.
3
Determine traction-preserving vehicle control inputs
Maintain a firm, steady wheel grip, avoid applying brakes or downshifting rapidly, and gently reduce throttle.
Abrupt kinetic force changes (hard braking, sudden acceleration, or aggressive engine braking) exceed the minimal friction threshold of black ice, initiating a wheel lock or slide.

Key Concept

Identifying black ice indicators and executing zero-abrupt-input hazard management on frozen overpasses
Rate this question