Halber Tacho, half the speedometer, is the rule German driving schools teach for following distance. On highways and country roads, the gap to the car ahead in meters should be half the speed in kilometers per hour. At 80 km/h, that is 40 meters. Section 4 of the road traffic regulations sets the standard behind it. The distance must usually be large enough that a driver can still stop if the car ahead brakes suddenly. Learner drivers also memorize rules of thumb for stopping. The reaction distance is the speed divided by ten, times three. The braking distance is the speed divided by ten, squared. At 50 km/h, that makes 15 meters of reaction distance and 25 meters of braking distance. An emergency stop can cut the braking distance in half. At more than 100 km/h, a driver who keeps less than three tenths of the half-speedometer distance receives a fine of 160 euros, two points and a one-month driving ban.