I was just watching an episode of rescue 911 on youtube, where a pair of runaway boxcars collided with a car at a crossing (perfect T-bone too, what are the chances of that??) because the elderly driver and passenger had no indication that the cars were coming. No gates, bells or lights. They just drove onto the crossing and the boxcars hit them. Now I was under the impression that the warning signals were operated electrically. There is a current running between on the rails, and when the car/train drove onto that particular section of track, a circuit would be completed by the wheelset (kind of like with block signaling) thus triggering the warning lights. But, looking at this video, that does not seem to be the case.
Also, the video I was talking about can be seen here
Also, the video I was talking about can be seen here