Two trains collide near Salisbury - 31 Oct 21

[whole diary]

[JayMac]

Really got to feel for the driver. Must have been terrifying for him.

[a-driver]

Yes, looks like the root cause is wheel slide then.  Probably what most of us within the industry suspected.

Further investigations will no doubt check whether the railhead treatment plan for the location was appropriate and followed properly, and that the driver was driving the train up to the point of impact as per SWR^» (South Western Railway - about) instructions (and whether those instructions are appropriate).

I hope they look at the part TPWS^▸ (Train Protection and Warning System) played in the incident. Once the train passes the red the driver loses all control and is effectively a passenger. I’d be interested to know if the emergency brake application made the slide worse.

[ChrisB]

From the photos/pics I can find, the signal protecting the junction is well back before the tunnel & seems to be the other side of the A30(?) overbridge. A hecknof a long way to slide? Am I right? I understand that the speed limit from the BSK^▸ (Brake Standard Corridor (carriage)) direction is 50mph, and the damage I estimate must have been going almost as quickly on impact to carry the train that far into the tunnel

[JayMac]

Falling gradient too, I believe.

[IndustryInsider]

I wouldn’t describe that as a heck of a long slide at all, and I certainly wouldn’t want to make even the vaguest of guesses as to what speed the impact was based on a couple of photos!

[a-driver]

I wouldn’t describe that as a heck of a long slide at all, and I certainly wouldn’t want to make even the vaguest of guesses as to what speed the impact was based on a couple of photos!

I managed just under 2 miles several years ago with all wheels locked. Luckily plain track with no restrictive aspects, applied the brakes at about 60mph, a mile or so later, I hit the platform ramp doing 55mph.

What distance from a signal protecting a junction to the junction is safe, that would prevent incidents like this?

[DaveHarries]

From the photos/pics I can find, the signal protecting the junction is well back before the tunnel & seems to be the other side of the A30(?) overbridge. [...] Am I right?

You are indeed. A look at the street-level view from the A30 overbridge on Google Earth shows the protecting signal - SY31 - in one direction while rotating the image 180 degrees allows a small view of the location where the derailment and collision occurred.

Dave

[Mark A]

Thinking of Google Streetview, the condition of the cutting sides over the last ten years ago contrasts sharply with their appearance in, ok, 1970, which I know is a different era, but they were clear of scrub and trees (photo from Flickr). The allotments to the right are still there, but even they are now losing out as they too are shaded by the full grown trees at the top of the cutting.

The google streetview is from June 2015 and provides the human interest of a couple of people in orange hi-viz gazing at the tunnel approach.

Given the two converging lines, junction and tunnel, there's something to be said for returning the cutting sides to grass. (And there's a lot to be said for properly resourcing the Cardiff - Portsmouth, the Waterloo - Exeter and the Waterloo Bristol traffic flows so that they're not miserably capacity-constrained for decades on end and can contribute properly to underwriting the necessary work to the infrastructure. As Graham's said, simply ensuring useable connections between Waterloo-Salisbury and Salisbury-Bristol might quickly find passenger numbers rising to 240,000 a year. The reason it's not done is presumably that it would overwhelm GWRs^▸ (Great Western Railway) provision between Salisbury and Bristol...)

https://goo.gl/maps/25yDmdeDFB5fcz8s5

https://www.flickr.com/photos/96859208@N07/10873405094

Mark

_{Edit: replaced first link with shortened version - Red Squirrel}

[PhilWakely]

Leaves on the line then?

Or perhaps an insufficient number of RHTT^▸ (Rail Head Treatment Train) workings over that stretch of line in the days leading up to the collision?

The scheduled RHTT run for earlier in the day on Sunday was cancelled 'at the request of the train operator' and doesn't appear to have run in the days beforehand either. It would have passed through Tunnel Junction four times.

[TonyK]

I managed just under 2 miles several years ago with all wheels locked. Luckily plain track with no restrictive aspects, applied the brakes at about 60mph, a mile or so later, I hit the platform ramp doing 55mph.

Ouch!

A member of the in-law contingent managed most of a mile at the controls of a Blackpool tram some years back, including the on-road bit by the Metropole hotel, coming to rest by the Tower. All he could do was sound the horn. He didn't hit anything or anybody. It was ice, not leaves, but shows the effect of lack of adhesion. The big question was why it had never happened before in the previous century, given that the conditions on the day were far from unheard of.

[TaplowGreen]

Thinking of Google Streetview, the condition of the cutting sides over the last ten years ago contrasts sharply with their appearance in, ok, 1970, which I know is a different era, but they were clear of scrub and trees (photo from Flickr). The allotments to the right are still there, but even they are now losing out as they too are shaded by the full grown trees at the top of the cutting.

The google streetview is from June 2015 and provides the human interest of a couple of people in orange hi-viz gazing at the tunnel approach.



Mark

Blimey. I bet m'learned friends will already be mobilising given the way that vegetation has been allowed to proliferate with consequent leaf fall on the lines - assuming it's Network Rail land of course.

Similar scenes of hugely overgrown land near the railway all over the country of course. I wonder if this will catalyse NR^» (Network Rail - home page) to do something about it?

[grahame]

The scheduled RHTT^▸ (Rail Head Treatment Train) run for earlier in the day on Sunday was cancelled 'at the request of the train operator' and doesn't appear to have run in the days beforehand either. It would have passed through Tunnel Junction four times.

For posterity, here are extracts from that URL

[TaplowGreen]

Any idea why the train operator would ask for it to be cancelled?

[a-driver]

Any idea why the train operator would ask for it to be cancelled?

No driver, no operators, loco failure, set failure, redeployed elsewhere…..

[lympstone_commuter]

This cab-view video shows the state of the vegetation in the cutting west of the tunnel in 2015.

In this video, signal SY31 is passed at around 38:33 (having become visible at around 38:21), and the junction is passed at around 38:45.

https://www.youtube.com/watch?v=FLV_D2RHeMc