Friday, 1 March 2013

After Moorgate

Yesterday I wrote about the Moorgate tube crash. Today I want to look at what has been done in the years after Moorgate to try to ensure that a crash like it will never happen again.

Since the beginning of railways, railway safety has always been reactive. From every crash emerges new technology or new regulations to attempt to ensure that no incident of the same type can ever happen again. Moorgate was no different, and it quickly gave its name to a system of protecting trains entering terminal stations known as “Moorgate Control”.

Rolled out to terminus stations across the network after the Moorgate crash, Moorgate Control originally consisted of two or three measures, depending on the location. The two common measures were to install a speed-controlled signal at the entrance to the platform area, and then to place two or three speed-controlled trainstops without signals (known as “sleeping policemen”) down the length of the platform area. This ensured that a train travelling over 20mph would be “tripped” on a trainstop and brought to a halt before reaching the end of the platform, while trains travelling below 20mph could continue, but that it would have to continue to slow on a steady braking curve for the length of the platform. [For a detailed explanation of how trainstops and “tripping” works on LU, click here].

The third part of Moorgate Control was not installed at all terminus stations. It consisted of running the feed to the traction current in the platform area through resistors, ensuring that a driver would not be able to speed up again having passed the speed-controlled elements of the protection, because there would not be enough power available to do this. The system also often trips out, cutting all traction current in the area, if trains attempt to “wind up” (accelerate) when coming in to the platform. However, this method is not compatible with modern stock, being finicky as they are with low voltages, and so it is now only in place at Cockfosters on the Piccadilly line.

Moorgate Control was put in place by London Underground because the recommendation of the official report – that all lines be turned over to failsafe, automatic operation such as that on the Victoria line – was prohibitively expensive. It succeeded LU’s immediate response to the tragedy – forcing all trains to stop at platform entrance signals – which wrecked the timetable and caused late running and delays to many lines in the weeks and months that followed.

Unfortunately, London Underground already had safety systems in place for dead end sidings both in tunnel sections and in the above ground sections. These systems, consisting of speed-controlled trainstops, were put in place after drivers died in collisions with the end wall or bufferstops at Tooting Broadway and Rayners Lane. It was never thought necessary to protect terminus stations in the same way, as it was thought the drivers in those two cases had failed to stop after mistaking the siding for the mainline. The official report in to the Moorgate crash apportioned no corporate blame to LU whatsoever, despite explicitly mentioning the protection put in place after Tooting Broadway and Rayners Lane.

While London Underground learnt from Moorgate, British Rail did not. Unprotected trains continued to collide with bufferstops, most notably at Canon Street in 1991 which resulted in the death of two passengers. It also resulted in the Transport and Works Act 1992, which made it illegal for railway workers to work while under the influence of intoxicating substances, because the driver was found to be a habitual user of cannabis. Protection in the form of AWS and TPWS only became the norm on British Rail in the wake of the Ladbroke Grove and Southall crashes in the 1990s.

So there you have it. On London Underground, protection for terminus stations was put in place in the wake of the Moorgate crash and on the manually driven lines, it still takes the same format. Three lines are now fully automatic, with the Northern line in the middle of a conversion process which should be complete by next year. By the time the Bakerloo and Piccadilly lines are finally converted to automatic running, probably in the 2030s, it will be over sixty years since Moorgate and the recommendation to protect the travelling public through automation.


Tom Scopes said...

Fascinating, you had explained the benefits of automation to me in the past, but I had never realised it was a reactionary measure, I guess I had mistakenly believed LU to be proactive with new technology.

Chris said...

Hey mate. LU was proactive, the Victoria line was the first automated railway in the world. It was in the wake of the Moorgate crash that the official investigator recommended that now LU had proved how safe automatic running on the Victoria line was, they should act to automate all lines. The report specifically mentions the Victoria line as being a safe model to follow.