[crocal]

Actually no. Cannot be too big and automatic. You need to allow a stranded car to break free. You must not crush a car that is only half way in.

Sigh.

Railway crossings are pure evil. There is no fail safe design that I know of without adding a proximity sensor inside the car (I am a railway signalling engineer). Would love to be wrong though.

[rexpress]

In the UK many crossings have full width barriers, and must be confirmed to be clear of road traffic after the barriers have closed before the protecting signal can be cleared for a train. These are effectively fail safe.

Confirmation comes from observation by a signaller or crossing operator either directly or by CCTV, or automatically by LiDAR and radar. These crossings tend to be used in areas of heavy road, pedestrian or rail movements, and when train speeds may exceed (from memory) 100 mph / 160 km/h.

Their disadvantage is additional installation, maintenance and operational costs. They must also be closed for longer before a train arrives than an automatic half-barrier crossing to allow for the required safety checks and ensure that signals are cleared far enough along the line that approaching trains do not need to slow down.

[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.