Level Crossings - Part 5
Since I last wrote on this subject (in Newsletter 54 ) there have been some developments. Network Rail's trial of shorter half-barriers started in April and will run for three months. The trial is taking place at both AOCL (automatic open [crossing], locally monitored) crossings in Ardrossan. In essence the crossings will look almost the same to a road-user as a normal AHB (automatic half barrier [crossing]) - with flashing lights and a barrier lowered to stop vehicles entering but not leaving the crossing. (This allows a safe escape for a vehicle caught when the barriers descend.) The train driver will continue to see a white light, indicating the crossing warning sequence is working correctly. It will remain the train driver's responsibility to ensure that it is safe for the train to proceed.
If all goes well and the trials do not uncover unexpected problems it is NR's intention to upgrade all 23 AOCLs in Scotland to the new style, likely to be called AHBL (the L indicating, as before, that the crossing is monitored locally, i.e., by the train driver) - another first for Scotland. The conversions, which at around £100,000 a time are a lot cheaper than full upgrade to AHB at three or four times as much, should all be completed within a couple of years. NR is expected to upgrade the more sensitive AOCLs first - presumably this will include Halkirk, Hoy, Delny and Bunchrew in the early phase.
The reason why an AHBL is so much cheaper is because its installation requires no change in the signalling arrangements. Making the train driver responsible for a safe crossing means that expensive electrical work is unnecessary - the machinery for lowering and raising the barriers is not connected to the signalling but is powered locally from the same source as the flashing lights. Because most of the roads are narrower than the standard highway it is possible to use rather shorter - and thus lighter - barriers, also helping to keep costs down.
All this was made clear at a HITRANS Rail Seminar held in Inverness on 30 March, where questions included (from me), "Will you do something about the open crossings like Kildonan?" An encouraging, if imprecise, reply was given by NR. Once all these improvements have been installed there is a good chance that line speeds may be raised at all the new AHBLs, assisted perhaps by some kind of obstacle detection (as is commonly used in Europe). On this last point nothing appears to have been decided pending the outcome of the trials.
Mike has written a series of articles over several years about level crossings:
Explanation of level crossing abbreviations
- AHBC = Automatic Half-barrier Crossing
- ABCL = Automatic [full] Barrier Crossing, Locally Monitored
- AOCL = Automatic Open Crossing, Locally Monitored
- AOCL+B = Automatic Open Crossing, Locally Monitored to which a barrier has been subsequently added
Locally monitored means there is a signal for train drivers to confirm the crossing is set and they have to confirm visually that it's safe.