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Monday 3 August 2020

The Railway’s Track Machine Problem

The report last February only made the Wandsworth Guardian: “A safety investigation has revealed that a train came within 75 seconds of potentially crashing in Wandsworth after a ‘serious operational irregularity’ … Shortly after 7pm on April 20 last year, a tamping machine was mistakenly driven onto a line which had not been closed to trains during the maintenance work … It crossed a junction through which a Southern train from London Victoria to East Grinstead had passed just 75 seconds earlier”.
One of those innocuous looking track machines

It’s never news until it stops being a near miss, by which time it’s too late to learn the lessons. More and more work on rail networks across Europe is being undertaken by self-propelled track machines. They look insignificant, but account for a lot of incident and accident reports. Safety standards, for those working these machines, sometimes slip.
4005, the unit involved in the accident, at Porto Campanhã, October 2007

What happens when they do slip, and it stops being a near miss, was illustrated in grim fashion last Friday near the Portuguese town of Soure. The area has a wayside station on the north line running from Lisbon to Porto; this has a loop line where slower trains can be stabled while faster ones pass. Slow as in self propelled track machines.

On Friday afternoon, a track machine reporting as VCC105, en route from Entroncamento to Mangualde on the Beira Alta line, was signalled into the loop at Soure, after passing Signal S1 (see diagram). The crew would be familiar with the move; their charge might manage 75km/h, while the line was cleared for a maximum speed of 190km/h (118mph).
VCC105 arrives at Soure and is looped

That speed is possible because of two things: a modern signalling system, and what is colloquially known as CONVEL, a train protection system that prevents passing danger signals, and overspeeding through points and crossings, through sharply curved track, and in busy station areas. The track machine was brought to a stand in the loop.

That occurred at 1512 hours. Just after 1524 hours, Signals S1 and S3 cleared to allow train AP133, set 4005 working the 1400 hours Alfa Pendular service from Lisbon to Porto and Braga, to pass. Despite the continuing lockdown, the train was well filled, with over 200 passengers on board. At this moment, the crew of VCC105 made their fateful mistake.
VCC105 comes to a stand in rear of Signal S5

It seems they misread Signal S3 as clearing them to go - for reasons that will become apparent, we will never know for certain - and moved off, passing Signal S5 (their signal, which was at danger). The effect of this was to trip the main line signals back to danger, but AP133 had already passed S1 and was bearing down on Soure station at line speed.

You may have wondered how VCC105 managed to pass S5, as trains have CONVEL. But track machines don’t have CONVEL, despite incidents involving passing signals at danger having happened before. No money in the budget (budget constraints also affect Network Rail - some staff in the Wandsworth incident were working from home).
Signals S1 and S3 clear for AP133; VCC105 moves off

At a speed of 190km/h, the driver of AP133 had very little time to react; there was an emergency brake application. The last thought the crew of VCC105 processed was probably the realisation that the points were not set for them, but for the main line - just before the 300 tonne mass of AP133 slammed into their machine, propelling it another half a kilometre up the line. Both those aboard VCC105 died in the accident.
The point of impact

Remarkably, all six coaches of AP133 remained upright with passenger compartments intact, although the leading vehicle was parted from the rest. 169 passengers received no injuries at all; there were three seriously injured. The driver of AP133 was gravely injured.

It is a testimony to modern rail passenger vehicle construction that the outcome was not worse. And while trains around south London tend not to run at the speeds involved in the Soure accident, the trains are often packed out, increasing the possibility of injury, or worse. Thus the lesson of just how innocuous those little track machines really are.

And in the UK and elsewhere, remember, it’s only news when it isn’t a near miss.
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grim northerner said...

In the early days of industrial capitalism, workers were routinely sucked into or caught on moving parts of machinery and killed. I have always thought of societies tolerance of daily inevitable death during the commute to work as the modern equivalent. How much gdp would be lost if cars were restricted to non fatal speeds and train safety Increased?

Anonymous said...

The loop should have had trap points, or no vehicles not fitted with CONVEL allowed on the line except with a full possession.

The Wandsworth incident was a case of non railway oriented staff ignoring basic railway rules, like obeying signals! A competent railwayman should have been aboard!

Jonathan said...

Why does it always take a disaster or several before safety features are added ?
I don't know much about the railways, but have a friend who lost several colleagues at Grayrigg in Cumbria..

Safety saves money in the long run and more importantly lives in the short term

Anonymous said...

Of course the incident actually happened at Balham. A competent railwayman would have made sure he knew exactly what was happening before doing anything, not set off in hope!

I was told once to pass a signal at danger because of a points failure, on approaching the points at walking pace because they didn't look to be set right I saw the signalman, who had had to clamp the points himself because of an S&T go slow, had incredibly clamped them the wrong way. I wouldn't have been derailed but it would have stopped the job on a busy commuter line for the rest of the day! Being clear about instructions, obeying signals and reading points was second nature, today it seems people are let lose on the railway without the required mindset.

grim northerner said...

Individuals with the right mindset will be filtered out by the hr dept no doubt.

Anonymous said...

Not wrong!