Another transportion item, because last night the train I was on hit a car stalled on the tracks (the occupant is OK, though was hit by the car when the train bashed it.)
Since trains do hit things, why aren't solutions to this more common in our data network world? A laser detector over the grade crossings would be simple enough.
At dinner, my friend Kurth Reynolds made a suggestion that I have improved. How about a small robot, equipped with camera and other sensors, which travels far enough in front of the train that if it sees a problem on the track, can send a signal back to the train in time to stop it. Trains take a while to stop, which is one of the reasons they can't do anything when they see a car or person ahead on the tracks.
You can't be too far ahead or you enter the "space" of the earlier train on the track, though during any tight conflicts you can of course give up this "foresight" and bear through (or slow down.)
If you have a human driving the train, you can show them video of what's ahead of the robot and give them time for a decision. Some decisions (Robot hits something or derails) would be automatic. Of course the robot might hit the car stalled on the tracks (though it can stop much, much faster than a train) but do far less damage.
The robot would be tall enough to go over the suicides who are "sleeping" on the track, but light enough so a car hit by it would survive.
Simpler for shorter runs like commuter trains would just be cameras along the track beaming to the oncoming trains. The engineer could be seeing a mile ahead at all times. Hey, if x10 can sell 2 broadcasting video cameras for $80 (WARNING: Don't buy from their web site, you will be spammed to death) I bet this can be made affordable.
This is important because some people don't think we should have rail with grade crossings. Without grade crossings, rail becomes vastly more expensive.
Some updates five years later: Some have worried the robot could hit workers or cars. Today, we are more comfortable we can build robots which would use LIDAR and never hit anything that wasn't running onto the track. The robots would also be light and perhaps have airbags to soften the blow against something rushing onto the track. When coming to a grade crossing, the robot would actually stop at the crossing and wait for the guard to come down (for the train, if the path is clear) and continue to monitor the crossing and report if something stops in it. Then it would speed up again and start going down the track to assure it is far enough ahead of the train.