You are driving on a narrow road. About 20 m ahead of you a child suddenly runs onto the roadway. When is a collision unavoidable despite emergency braking?

In German traffic rules, the stopping distance depends on your speed. At 50 km/h, the total stopping distance (reaction distance plus braking distance) is generally around 25-28 meters. Since the child appears about 20 meters ahead, even if you brake immediately, you won't have enough distance to stop in time and avoid a collision. At lower speeds like 30 km/h or 20 km/h, the stopping distance is much shorter, so you would likely be able to stop before reaching the child. This is why a collision becomes unavoidable at higher speeds like 50 km/h when the obstacle appears suddenly and close.