[jcrawfordor]

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.

[bobthepanda]

Trains are very heavy and have long braking distances at speed, in some cases over a mile. For a train to have enough time to stop, the crossing would have to be kept clear for a very long time, which would probably tempt drivers to bypass the gates since they would perceive the crossing to be overly safe (described in the article as the "cry wolf" phenomenon).

[rexpress]

Googling "MCB-OD crossings" will bring up various pages and videos that show such crossings in the UK. They are relatively new to the UK but I believe they have been used for some time in continental Europe.

They have disadvantages including expense, and additional road closure times (compared to automatic half-barriers) as they must be closed and proven clear early enough that an approaching train does not need to slow down.