I know that at least in this area some wyes and crossing points use radar (the same type used for lane occupancy on roads) as an additional safety measure---something like track circuit clear but radar detection of an object results in a very restrictive signal like a "red-yellow." Do you know if there's a reason why this hasn't been deployed for road crossings? Definitely it wouldn't be perfect but seems like it could help with stuck-vehicle scenarios, especially in more urban areas where speeds are low but visibility is poor. I guess I assume that the reason it isn't being done is because it would require some kind of upgraded cab signalling that would cost too much to roll out.