General Knowledge · Hot Weather Driving
Why does very hot weather create a road-surface hazard called "bleeding tar"?
1.Extreme heat causes tar in the road pavement to rise to the surface, and the spots where it does are very slipperyCorrect answer
2.Extreme heat causes asphalt to expand and crack, opening potholes that can damage a tire or a wheel rim at highway speed
3.Extreme heat melts the road paint used for lane markings, making lane positions hard to make out at a distance
4.Extreme heat causes tar to give off fumes that reduce visibility for the drivers following behind
Explanation
Bleeding tar happens because very hot weather causes tar within the road pavement to rise to the surface, and wherever it surfaces the pavement becomes very slippery. This hazard sits within the required-knowledge area named by 49 CFR 383.111(a)(12)(ii) ("hot weather"), which names the topic but does not itself describe this specific hazard, so it is standard driver-training content. The wrong options fail for a shared reason: each describes a real category of pavement or visibility problem, cracking, faded markings, or fumes, that is not what "bleeding tar" refers to, so none identifies the actual mechanism of this specific hot-weather hazard.
Source: 49 CFR 383.111(a)(12)(ii)
Related Hot Weather Driving questions
- A driver checks a tire during a stop in extreme heat and finds the measured air pressure is higher than the vehicle's specified cold inflation pressure. What does 49 CFR 393.75(i) say the driver should do?
- What is the safe procedure for checking engine coolant on a vehicle that does not have a sight glass or coolant recovery container, after driving in very hot weather?
- In desert conditions during very hot weather, why does guidance advise driving slower than usual, apart from any posted speed limit?
- While driving in very hot weather, the coolant temperature gauge climbs above the highest safe mark on the gauge. What should the driver do?