OBSTACLE DETECTION CROSSING
This one has a footbridge, so we stand on it to get the best view of the crossing. It’s already clear that this one is rather more advanced than the others we’ve seen today.
Says Wake: “You see that thing that looks like a giant Tic-Tac? That’s a radar obstacle detection system. So when you hear people referring to an OD crossing, this is what they are talking about.”
The giant Tic-Tac does a radar sweep to check if the crossing is clear. If it is, the barriers will come down. If not, it will do another sweep. It will do this three times if necessary. If the crossing is still not clear, it will then alert the signaller (in this case at the local Three Bridges control centre).
The radar sweeps at half a metre from the ground, which isn’t very low - a person could crawl underneath that quite easily, or fall over and be missed by the sweep. So there is an upper LIDAR (Laser imaging detection and ranging) and lower LIDAR to fill in the gaps missed by the radar and detect any obstacle up to about eight inches high. The lower scanning was the system that made the headlines back in 2014 ( RAIL 740) for detecting a hungry group of crows rummaging through a discarded Kentucky Fried Chicken Bargain Bucket that had blown onto a crossing on the Breckland Line. At the time, the system could only report that ‘something’ was causing an obstruction.
Wake explains: “There were a lot of teething problems with this technology that
were originally blamed on the KFC container. Many turned out to be problems with the relays from the equipment. They’ve been improved an awful lot since!”
Only when the sweeps are completed successfully will the approaching signals clear. “One obvious defect with this type of crossing, where there is a continuous stream of users, is that people realise they can cross unhindered because the barriers won’t come down. If they do come down as people cross, they’ll sense the obstruction and go back up. So people just carry on crossing.”
Wake says that CCTV cameras are installed in places where this is likely to occur, to catch people misusing the crossing.
Despite having a footbridge, the crossing also features a footpath. People always take the shortest path, so they only use the footbridge when the barriers are down. But, of course, disabled users and those with pushchairs or difficulties using stairs would wait for the barriers to lift anyway.
Nothing seems to be wrong with this one, it’s a pretty perfect example of a high-tech solution for a busy location.
Our last crossing inspected, notes made, photographs taken and boots suitably muddied, we head back to base. I hadn’t expected that an inspector’s life would involve quite so much time out on the ‘real railway’. Wake reminds me that it’s not always like this. But the time they spend out of the office, seeing how things work in practice is invaluable in ensuring that crossing safety is not just a statistic on paper, but something that protects you and I every time we cross the lines.