To be able to observe better.

The following is stated in the traffic rules:

Before crossing a level crossing, road users shall ascertain whether or not a train or tram is approaching. This applies even if the level crossing is specially safeguarded. Drivers shall drive at a sufficiently low speed for it to be possible, if necessary, to stop at a safe distance from the crossing.

The point here is that you should drive at a sufficiently low speed so you can observe and stop, if you see a train or tram approaching.

Also be aware that you must give free passage, and if necessary stop, for trams and trains. Also be aware that you must give free passage, and if necessary stop, for trams and trains.