Some map races are at night and it seems that there is no or very little change in the time of day of those races, unlike some others that change from day to night, and vice versa, on re-running them. Because the tracks in GC are very twisty, the cars are very fast, the cars' headlights are weak, and street lights are nonexistent or weak, races at night are very hard to win. But turning on the optimal racing line shows critical information about braking and turning before a corner is visible. That makes a big difference, as it helps to avoid braking too little, too much or too late and to avoid turning too little or too late.