Because the stopping distance of the train is quite extensive and when traveling at a high speed the stopping distance can be even more than 1,000 meters.

Because the traveling course of the train can not be changed suddenly, the train does not have a steering mechanism and the locomotive engineer can not divert the train from its course.

Because the train is closer and faster than what it seems to be, even when you can see the train it is difficult to estimate when it will pass you by.

Because the train is very quiet, it can not be heard from afar. Even if a train whistle is heard, it is possible that a second train is approaching that has not sounded its whistle.

Because the trains travel in both directions, even if one train has already passed the crossing, it is possible that another train is approaching from the opposite direction.

Because the train schedules are liable to change, even if you are familiar with the scheduled times of the trains at the level crossing – you can never know when the next train will pass the crossing.