Driver's License Test Prep
Pennsylvania Practice Defensive Driving

At what speed does the manual say a vehicle can begin to hydroplane on a wet roadway?

  1. A.
    As low as 45 mph
  2. B.
    As low as 55 mph
  3. C.
    As low as 25 mph
  4. D.
    As low as 35 mph Correct
The Why

The answer is "As low as 35 mph"

The Hydroplaning section warns that a vehicle can begin to hydroplane at speeds as low as 35 mph when water is only one-tenth of an inch deep; faster speeds and worn tires make the risk worse. Drivers who picture hydroplaning as a freeway-only hazard overshoot the manual's threshold and land on B's interstate-speed figure.

Why the others miss

The traps in the wrong answers

A. As low as 45 mph

The manual's threshold is lower than this. Guesses a number close to typical suburban speeds rather than the actual figure the manual publishes.

B. As low as 55 mph

The manual sets a much lower threshold. Assumes hydroplaning is a freeway-only risk tied to interstate speeds, so overshoots the actual number.

C. As low as 25 mph

The manual sets the threshold higher than this. Anchors to the 25 mph number the manual uses in a separate rule about steering versus braking.

The Rule

This question tests your knowledge of Defensive Driving in Pennsylvania. Source: Pennsylvania Driver Manual, "Hydroplaning," p.40..

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