You press the brake pedal on a long downhill grade and it sinks to the floor with no resistance. What is the first thing you should do?

Why D is correct

A pedal that sinks to the floor usually means either fluid loss or brake fade from sustained braking on a long descent, and the opening move covers both: pump hard and fast, because pumping can rebuild enough pressure for one firm stop and it is worth trying before anything else. If nothing builds, shift down one gear at a time and let engine compression do the work — that is what a lower gear is for on a descent in the first place. The parking brake comes last and goes on gradually; hauling it on locks the rear wheels and starts a skid you cannot recover at speed. If none of it works, look for an escape ramp or an uphill turnoff and clear traffic with the horn.

Why the other options are wrong

A. Switch off the ignition and coast to a stop

Switching off the ignition also kills power steering and, once the key turns far enough, locks the column. With the power assistance gone you face a heavy wheel at exactly the moment you most need precise control of it.

B. Pull the parking brake fully on at once

Yanking the parking brake locks the rear wheels and starts a skid, and most hand brakes are not built to hold highway speed anyway. The whole point of applying it gradually is to keep the car going straight while it slows.

C. Steer into the guardrail to scrub off speed

Deliberately hitting a guardrail is a last resort after everything else has failed, not an opening move. A controlled stop using engine braking and gradual parking brake pressure is far safer, and there may be an escape ramp ahead.

On the road

A loaded car descending a long mountain grade rides the brakes the whole way, which boils the fluid and leaves nothing when it is needed. The driver who uses a lower gear and short firm brake applications arrives at the bottom with working brakes; the one who rode them does not.

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