I know that trams can be done in two ways - Simutrans classic and TTD. It may be problem. Also I know that it may be done (but not in the most perfect way) with rail crossing. But I have idea: Priority for trams on crossings. Currently if tram track is over road (may be for someone build tram track over road), cars can go through trams - like they would be ghosts.
It is not really good situation. For correction of this I call that lights (that are for cars) should be accepted by trams too. Still it would not be perfect solution (because in some directions they would cross each other too), but something is better than nothing.