You can get into some pretty nasty train wrecks if you try hard enough.
Thing is, modern locomotives and rail systems have multiple safety-nets that prevent this from happening. Railway signals will notify you if you should slow down or come to a complete stop in case there's a hazard up ahead. In the event that the train operator doesn't stop or slow down to the appropriate speed, an on-board computer will actually override the controls and apply the emergency brake automatically, and the only way to resume operation is to wait for the train to come to a complete stop.
Road crossings function automatically, so you have no control over whether the gates come down or not. And the game doesn't have "random cars getting stuck in the middle of the tracks, and subsequently getting pwned" programmed in.
...but yeah, you can still get into some wrecks.