Severn Tunnel: Comparing road and rail

[whole diary]

[simonw]

The argument that justified the second Severn bridge also justifies an additional rail link. More capacity is needed. 2 Intercity trains per hour and a local train per hour (6 crossings) is about its limit. At peak, more trains are needed.

My initial observation is that the DfT^» (Department for Transport - about) experience of maintaining the M5 Avon bridge, directly led to the decision to build a second Thelwell Viaduct (bridge) to allow the original to be fixed. The result is that there is now more capacity to cross the River Mersey via M6.

The ongoing maintenance of the Severn Tunnel is now reminiscent of the 10 odd years of road works to the M5 Avon bridge. If so, does the cost of maintaining the tunnel whilst keeping it open exceed the cost of building an alternative and repairing the tunnel at leisure?

The cost of the second Severn Bridge is funded by a toll, why could no a second severn rail crossing also be funded by a toll? Then again, surely the ^1000 million that FGW^▸ (First Great Western) are paying the DfT for the privilege of running the franchise could pay for such a crossing.

[eightf48544]

The cost of the second Severn Bridge is funded by a toll, why could not a second severn rail crossing also be funded by a toll? Then again, surely the ^1000 million that FGW^▸ (First Great Western) are paying the DfT^» (Department for Transport - about) for the privilege of running the franchise could pay for such a crossing.

I am afraid that you misunderstand the way the Treasury works. The ^1000 million FGW has to pay is not for rail improvements it's just part of general government revenue. It can't be allocated to building a new rail crossing of the Severn as that would be hypothecation which the Treasury doesn't allow. It's also why all the tax collected off motorists doesn't go towards building new roads or even maintaining the existing ones.

I see a bridge has been suggested, the problem with the Severn is unless you go upstream of Sharpness you need a suspension bridge to span the width and to give the necessary clearance for shipping. Also I didn't think you could run a railway over a (long) suspension bridge because to stay up they have to sway which would distort the tracks. Further having sailed a narrow boat in both directions from Sharpeness to Portishaed the tidal flow is awesome and would make building any piers for a ridgid bridge in the full flow almost impossible. Don't forget Avonmouth has the second highest tidal range in the world. But even if they could be built they would be extremely vunerable to being hit by quite large ships as the origanl Severn and Wye bridge at Sharpness was. You only have to think of one of the car carrying floating bricks that serve Royal Portbury losing it's engines on the approach to the Dock and being swept upstream.

You could build a new bridge to replace the old Severn and Wye bridge from Sharpenss to Lydney, which was destroyed in a tragic accident in the 60s, when two petrol  barges missed entrance to Sharpness dock in fog and were swept upstream by the tide, and hit the bridge and blew up. Up to it's destruction  it was used for diversions but as the largest engine that could be used was Dean Goods or equivalent most Expresses went via Gloucester as now.

Even if it was built it would be a long way round with slow approaches unless say you built a new line from west of Sodbury tunnel across to Sharpness and really fettled up the old South Wales mainline west of Lydney for 125 mph. It's  pretty well alinged already as it's a Brunel route and virtually level running beside the river. The new link could have junctions with the Midland where it crosses probably somewhere near Berkley.

But it would only be of any real use for London services, but still it would free up the tunnel for local services.

However I still say it's a tremendous inditement of the 5th largest economy in the world that we can't "afford" a second Severn tunnel.

[smokey]

Seems Stupid to have ever have got RID of the Severn Rail Bridge, OK it had been Damaged but BR^▸ (British Rail(ways)) had drawn up plans to repair the bridge with a Double length Span so not having to rebuild the Damaged Pier.

[Chris from Nailsea]

Thanks for that background information, smokey!

There's also some useful information at http://en.wikipedia.org/wiki/Severn_Railway_Bridge and http://www.bbc.co.uk/gloucestershire/focus/2004/10/sharpness_rail_disaster.shtml

[Trowres]

I see a bridge has been suggested, the problem with the Severn is unless you go upstream of Sharpness you need a suspension bridge to span the width and to give the necessary clearance for shipping. Also I didn't think you could run a railway over a (long) suspension bridge because to stay up they have to sway which would distort the tracks. use for London services, but still it would free up the tunnel for local services.

However I still say it's a tremendous inditement of the 5th largest economy in the world that we can't "afford" a second Severn tunnel.

The so-called Second Severn Crossing runs parallel to the Severn Tunnel. It is not a suspension bridge. Maybe one day when petrol reaches ^2 a litre it will seem a bit wasteful to have six traffic lanes across it, and a couple can be used for other purposes. Its gradient profile might not suit heavy rail, but South Wales - Bristol LRT?

Curiously, I can find no reference to the weight restriction on the Second Severn Crossing. Anybody with this knowledge?