Last month, a significant achievement took place on the Crossrail project, which is far more important than the headlines make it seem to be.
At a basic level, the Office of Rail Regulation approved the use of the new Class 345 trains that will be used on the Elizabeth line to carry passengers into the Heathrow tunnels.
The delay has been caused by the bane and saviour of modern railways, the signalling system.
Modern trains are more like computers on wheels, which is great for running a highly intensive service and improving maintenance reliability but does also mean that an awful lot of what happens in a train is now controlled by a central brain – the Train Control Management System (TCMS).
This in turn talks to the signalling systems to direct where the train should go – with a human up front of course — but getting the two to work together is sometimes harder than expected.
Crossrail even looked at adding the now obsolete GW-ATP signalling system used in the Heathrow tunnels to its trains to get around the problem but concluded it was not viable due to the age of the technology being used.
A lot of the problems are down to getting the modern train controls to talk to the different and overlapping radio signals used by railway signalling systems.
When you have lots of legacy signalling systems on the National Rail network, and the GW-ATP signalling system, one of the roles of the software is to filter away the noise to get just the information it needs. In the very old days had such a thing existed, it would have meant physically changing crystals in the radio kit. Today the hard work is done in software, so it’s a lot easier to update the software and test again to see if that works.
On top of that is all the testing to try and break the system, and ensure it doesn’t break, and that redundancy back-ups kick in as expected. And every time they update the software, they have to check that the tests they previously passed haven’t now failed.
It’s just taken a lot longer than expected to get the software to the point where it is safe for passenger use.
As it happened, that milestone was just about to be achieved as the lockdown took place, but being software, a remote upgrade was possible, and that was the final stage needed to get the regulator’s approval.
To a degree, this is a rather dry academic regulatory issue – nice to have, and it does move the Crossrail project on an extra step.
However, it’s a much bigger issue than it sounds. This is the next generation of train control systems, and the only place it’s been used before in the UK was for testing the technology on a line through Wales, the Cambrian line.
To deploy this new system on a part of the rail network that’s as complicated as the Heathrow to Paddington line is quite a substantial achievement.
Crossrail’s Technical Director, Colin Brown told me a couple of weeks back that due to the sudden lockdown, they hadn’t expected to get the regulatory approval, but they had managed to complete enough testing and validation for the approval for the latest software build, and now the trains are finally authorised for Heathrow Airport.
When the line is fully operational, a total of six Elizabeth line trains per hour will serve Heathrow Airport. Four will go to Terminals 2, 3 and 4 and two will go to Terminals 2, 3 and 5. This will also increase services to Ealing Broadway, Southall and Hayes & Harlington.
For all the headaches, the new signalling and train control systems offer a lot of benefits, from very tight adherence to the timetable, the ability to run the trains closer together to get the intense service being planned, operating the in-train air cooling and information screens, to controlling platform doors in stations.
To my mind though, the neatest trick is one that only the drivers will ever see.
Around half of westbound trains will terminate at Paddington, but to head back eastwards, once all the passengers are off, they carry on westwards to Westbourne Park, then return back to Paddington on the eastbound line.
Normally that means the train driver would drive to Westbourne Park, stop, walk through the train to the other end, then drive back. But with “auto-reverse”, as soon as the train leaves Paddington, the driver switches to automatic and starts walking through the train to the other end. By the time the train arrives at Westbourne Park sidings, the driver will be sitting in the drivers cab at the other end of the train ready to head back into Central London.
Now that’s really quite clever.