What drivers used to know - anticipatory downhill driving
For the modern driver, uphill and downhill gradients are no reason to take special precautions. The brakes of modern cars can cope with prolonged braking and modern automatic gearboxes even automatically downshift to a lower gear to utilize the engine's braking power.
Things were very different in the past. Not only did the brakes tend to fade early on if they were applied over long distances, but the engine had hardly any braking effect in top gear, which might have been engaged on the top of a mountain pass.
An old driver's rule was therefore that you should drive down the mountain in the same gear as you drove up it. In many cases, this was even second or first gear, as cars were no rockets uphill either.
Of course, caution was required when changing down, as the car was in danger of speeding up when idling (when accelerating). That's why prudent people applied the handbrake before downshifting, so that if you couldn't engage the gear, you didn't suddenly accelerate to too high a speed in neutral. After the shift maneuver, the handbrake was of course released again. All this might have happened at 20 or 40 km/h, because you didn't go down a hill much faster than that. This is also completely unthinkable for modern drivers.
