Speed, stopping distance and vehicle control
Speed questions test more than the number on the sign. You must know the general limits, choose a safe speed for conditions, and calculate or estimate stopping distance using reaction distance plus braking distance.
General limits and safe speed
In Denmark the general limits are 50 km/h in built-up areas, 80 km/h on rural roads and 130 km/h on motorways; a motortrafikvej is generally 80 km/h unless signed otherwise. Signs can lower these limits, and roadworks, schools and residential areas often do. A limit is a maximum, not a target: rain, fog, ice, darkness, traffic and poor visibility can make a lower speed the only safe one.
Stopping distance
Total stopping distance = reaction distance + braking distance. With a reaction time of about one second, reaction distance is roughly speed in km/h divided by 3.6. A useful dry-road approximation for braking distance is (speed ÷ 10)² metres. Wet roads roughly double the braking distance; ice and snow can multiply it several times. ABS helps you steer under heavy braking but does not shorten the stopping distance. Keep at least a two-second gap in good conditions and more in rain or poor visibility.
Vehicle control
Use engine braking and the brakes together on long descents; do not coast in neutral. In aquaplaning, ease off the accelerator, keep the steering steady and avoid sudden braking. On icy roads, brake gently and steer smoothly. Choose a gear that gives control rather than maximum speed.
Worked example
At 80 km/h, reaction distance is about 80 ÷ 3.6 = 22 m. Dry braking distance is about (80 ÷ 10)² = 64 m. Total stopping distance is therefore about 86 m. On a wet road, allow roughly 1.5 to 2 times that braking distance, so the total is well over 100 m. At 50 km/h the same calculation gives about 14 m reaction plus 25 m braking, about 39 m total.
Traps
Quoting only the braking distance; believing ABS guarantees a shorter stop; tailgating at the speed limit; and treating the limit as a safe speed in fog or rain.