In motorsport, like the ideal line, the battle line is the path that a driver chooses around bends on a racetrack in order to defend his position against a competitor directly following. Driving on the battle line is slower than driving on the ideal line, but blocks the most favorable path for the competitor to overtake.
A vehicle that comes close to the vehicle in front is usually faster. This is due to the fact that it would hardly be possible to drive up close with a slower vehicle. In vehicles with efficient aerodynamics such as formula racing , this is disturbed by air turbulence when a vehicle is driving up close, the vehicle loses downforce and thus its grip. The beneficial effect of the slipstream can often only be used on the straights. Tight curves after a long straight are therefore often the best overtaking opportunities.
The faster man behind, who is driving up close, has the opportunity to overtake the man in front next to the ideal line - usually on the inside of the bend - by excess speed or braking later (" braking out "). To prevent this, the vehicle in front deviates from the ideal line in front of a bend and approaches the bend further inside so as not to leave any room for a competitor on the inside of the bend. An attempt to overtake on the sidelines is rarely successful, as the distance there is longer.
Because driving on the battle line is slower than driving on the ideal line, the man in front also loses time in a duel. The battle line is therefore usually only driven when a pursuer is preparing an overtaking maneuver. For the first in a race, the time lost is insignificant as long as the second does not pass. Position battles for rear seats, on the other hand, often lead to pilots driving further back suddenly being able to overtake both vehicles at the same time.
However, these conditions only apply to courses with flat curves. In steep turns , as they are often present on oval courses, for example , overtaking can be carried out inside and outside due to the elevation in the curves, so that a battle line is not possible.