Building rail lines over existing infrastructure

[Factotum]

A thought that came to me when observing the mass destruction been caused by providing a new route for HS2.
Why not go double decker over existing motorways?

Build large pillars each side of the road connected with a deck. Then lay a deck above and parallel to the roadway to carry the tracks.
On and off ramps for stations shouldn't be a huge problem especially for HS2 which has very few stations.
And the stations would be ideally placed for rail replacement buses

 

[JonathanH]

Why not go double decker over existing motorways?

Too much disruption to the road traffic and the gradients and curves may be too severe for a railway. Also, the road traffic may be more accident prone in what would effectively be a tunnel.

The height of the railway formation where it has to go above existing road junctions may also be quite a challenge.

 

[skyhigh]

Motorways don't tend to go through city centres. They also have a rather variable height profile, with gradients much steeper than trains like. The disruption to motorway users would also be immense and I'm sure the cost of building it that way would be significantly higher than doing it the way they've planned. In addition, the result would be a complete eyesore.

If you're suggesting HS2 should do this, you're also way too late to make such major changes.

 

[CW2]

HS2 did (briefly) consider running through the Chilterns parallel with the M40. It quickly became apparent that the minimum curvature for a design speed of 400 kph on rail is too far removed from that of a 120 kph road that your "parallel" routes only coincide briefly every 5 - 10 kms, with a large amount of "islanding" where land is cut off at both sides by the new route.

 

[The Planner]

A thought that came to me when observing the mass destruction been caused by providing a new route for HS2.
Why not go double decker over existing motorways?

Build large pillars each side of the road connected with a deck. Then lay a deck above and parallel to the roadway to carry the tracks.
On and off ramps for stations shouldn't be a huge problem especially for HS2 which has very few stations.
And the stations would be ideally placed for rail replacement buses

How do you deal with motorway junctions above the motorway, go higher? The amount of concrete required would blow what is currently being used out the water and that is used as a reason against its environmental credentials.

 

[D6130]

I would have thought that a much more environmentally-friendly way to build new high speed lines would be to do what has largely been done in France, Italy and Germany in recent years and build them alongside and parallel to existing lines or motorways, where the geometry of the latter permits.(Obviously the M40 would be an exception!) If HS2 had been planned to follow the M1 from London Northwards, then the Eastern arm to largely continue to follow it to Sheffield and Leeds, while the Western arm followed the M6 to Birmingham and the North-West, I think there we would be far less environmental distruction and therefore far fewer protests.

 

[swt_passenger]

I would have thought that a much more environmentally-friendly way to build new high speed lines would be to do what has largely been done in France, Italy and Germany in recent years and build them alongside and parallel to existing lines or motorways, where the geometry of the latter permits.(Obviously the M40 would be an exception!) If HS2 had been planned to follow the M1 from London Northwards, then the Eastern arm to largely continue to follow it to Sheffield and Leeds, while the Western arm followed the M6 to Birmingham and the North-West, I think there we would be far less environmental distruction and therefore far fewer protests.

IIRC it was looked at and ruled out very early on. Check out the M1 through Luton as an example of why it just wouldnt fit.

 

[Tomos y Tanc]

Adding a railway to existing infrastucture? Probably not a good idea.

Building new integrated road/rail infrastructure works though. A long section of the relatively new Mendurah line in Western Australia, for instance, acts as the median strip for the accompanying freeway.

 

[edwin_m]

I would have thought that a much more environmentally-friendly way to build new high speed lines would be to do what has largely been done in France, Italy and Germany in recent years and build them alongside and parallel to existing lines or motorways, where the geometry of the latter permits.(Obviously the M40 would be an exception!) If HS2 had been planned to follow the M1 from London Northwards, then the Eastern arm to largely continue to follow it to Sheffield and Leeds, while the Western arm followed the M6 to Birmingham and the North-West, I think there we would be far less environmental distruction and therefore far fewer protests.

I think most other motorways in Britain would turn out to be exceptions too. It only really works where the land is flat, the motorway is straight, and there are no settlements in the way. An obvious example is where the Eurostar follows a motorway for much of the way between Paris and Lille, but even here the separation tends to be 100 metres or so (probably to avoid junctions and minor curves), and the strip of land in between isn't much use.

 

[snowball]

A lot of the NE arm of HS2 is planned to run more or less alongside sections of the M42, A42, M1 and M18 but the distance between road and rail varies where the road curves more sharply than the railway. You can check the plans on the DfT website.

 

[AlbertBeale]

HS2 did (briefly) consider running through the Chilterns parallel with the M40. It quickly became apparent that the minimum curvature for a design speed of 400 kph on rail is too far removed from that of a 120 kph road that your "parallel" routes only coincide briefly every 5 - 10 kms, with a large amount of "islanding" where land is cut off at both sides by the new route.

Yet another reason why wanting HS2 to be 400 kph is absurd and vainglorious - and unnecessary - for a country this size. Many new lines in mainland Europe, though "HS", don't aim for such overkill in terms of speed.

 

[Dr Hoo]

A thought that came to me when observing the mass destruction been caused by providing a new route for HS2.
Why not go double decker over existing motorways?

Build large pillars each side of the road connected with a deck. Then lay a deck above and parallel to the roadway to carry the tracks.
On and off ramps for stations shouldn't be a huge problem especially for HS2 which has very few stations.
And the stations would be ideally placed for rail replacement buses

To the extent that HS2 will require actually require disruptive engineering possessions (bearing in mind that for many years it will be on a 'maintenance honeymoon' as a new railway and, being passenger-only, will have ample overnight windows for routine minor work) I would thought that the alternatives would be the classic lines. I haven't assumed that one would run buses from (say) Euston to Birmingham Interchange, rather passengers would be directed to a conventional train to Birmingham International.

 

[CW2]

Yet another reason why wanting HS2 to be 400 kph is absurd and vainglorious - and unnecessary - for a country this size. Many new lines in mainland Europe, though "HS", don't aim for such overkill in terms of speed.

It would have made very little difference if you halved the HS2 design speed to 200 kph, the difference between railway curve minimum radii and those applied on motorways is simply too great.
To be clear, the design speed of the open route sections of HS2 is set at 400 kph to allow for future developments in traction and signalling (given that once built it will remain for more than a century).
There is nothing "vainglorious" about a pragmatic engineering solution.

 

[JonathanH]

It would have made very little difference if you halved the HS2 design speed to 200 kph, the difference between railway curve minimum radii and those applied on motorways is simply too great.

To be fair though, the railway needs less width than the motorway so could take a 'racing line' above the motorway.

 

[30907]

I think most other motorways in Britain would turn out to be exceptions too. It only really works where the land is flat, the motorway is straight, and there are no settlements in the way. An obvious example is where the Eurostar follows a motorway for much of the way between Paris and Lille, but even here the separation tends to be 100 metres or so (probably to avoid junctions and minor curves), and the strip of land in between isn't much use.

And I recall the motorway had to be moved in places, and one service area resited, to allow it (I drove the A1 annually and remember the (relatively minor) disruption).

Yet another reason why wanting HS2 to be 400 kph is absurd and vainglorious - and unnecessary - for a country this size. Many new lines in mainland Europe, though "HS", don't aim for such overkill in terms of speed.

Some do, some don't - given that SNCF permit 330, RENFE 310, DB and TI 300, designing for 400 isn't excessive.

 

[Ploughman]

Instead of over road.
Double deck the railway.
Would this be a means of 4 tracking when space is tight? Manchester Oxford rd - Piccadilly for an instance.
Possibly Slow / stopping lines on the bottom with Fast non stops above.

 

[6Gman]

It would have made very little difference if you halved the HS2 design speed to 200 kph, the difference between railway curve minimum radii and those applied on motorways is simply too great.
To be clear, the design speed of the open route sections of HS2 is set at 400 kph to allow for future developments in traction and signalling (given that once built it will remain for more than a century).
There is nothing "vainglorious" about a pragmatic engineering solution.

Thank goodness the engineers who built the London & Birmingham and the Grand Junction * didn't say "no train will ever need to travel in excess of 40mph so we'll build it to that standard" . . .

* And other railways. Of course some railways are still limited by a spec which was considered fine at the time. Newton - Plymouth e.g.

== Doublepost prevention - post automatically merged: 10 Jul 2021 ==

Instead of over road.
Double deck the railway.
Would this be a means of 4 tracking when space is tight? Manchester Oxford rd - Piccadilly for an instance.
Possibly Slow / stopping lines on the bottom with Fast non stops above.

No.

How do you get up/down at each end?
How do you build it without massive disruption?
How do you placate the property owners alongside the route?

 

[Ianno87]

Thank goodness the engineers who built the London & Birmingham and the Grand Junction * didn't say "no train will ever need to travel in excess of 40mph so we'll build it to that standard" . . .

* And other railways. Of course some railways are still limited by a spec which was considered fine at the time. Newton - Plymouth e.g.

And imagine if France had said "well nobody else runs trains at 300kmh, so we won't either..."

 

[Mikey C]

HS1 does run along a lot of existing corridors, alongside the Tilbury line between Dagenham and Purfleet, alongside the A2/M2 between Southfleet and Bluebell Hill (indeed this section of A2 was rebuilt at the same time to a higher standard) before tunnelling through the hill to join the M20 near Detling, which it roughly follows to the Channel Tunnel, other than diverting to enter Ashford.

 

[edwin_m]

Instead of over road.
Double deck the railway.
Would this be a means of 4 tracking when space is tight? Manchester Oxford rd - Piccadilly for an instance.
Possibly Slow / stopping lines on the bottom with Fast non stops above.

It was briefly considered in a study into the Manchester rail network about 20 years ago, though I think it was putting both Up tracks above both Down tracks or vice versa, which would at least mean trains only needed a simple crossover to swap lines. But it never got seriously assessed, not least because the Metrolink viaduct would have prevented access to the routes via Ordsall Lane.

 

[Ianno87]

HS1 does run along a lot of existing corridors, alongside the Tilbury line between Dagenham and Purfleet, alongside the A2/M2 between Southfleet and Bluebell Hill (indeed this section of A2 was rebuilt at the same time to a higher standard) before tunnelling through the hill to join the M20 near Detling, which it roughly follows to the Channel Tunnel, other than diverting to enter Ashford.

HS1 is also sort of "double deck" in that it runs under the North London Line between York Way and Stratford.

 

[61653 HTAFC]

Now, if the suggestion was to reduce the motorway to a single carriageway with a significantly reduced speed limit, then use the vacated carriageway for a railway, you might be on to something...*

*= please note, this is NOT a serious suggestion.

 

[D6130]

*= please note, this is NOT a serious suggestion.

Oh, I don't know....you could be onto something there!

 

[snowball]

HS1 is also sort of "double deck" in that it runs under the North London Line between York Way and Stratford.

and HS2 will be sort of double deck where it runs in tunnel under existing lines between Old Oak Common and West Ruislip.

 

[Factotum]

Adding a railway to existing infrastucture? Probably not a good idea.

Building new integrated road/rail infrastructure works though. A long section of the relatively new Mendurah line in Western Australia, for instance, acts as the median strip for the accompanying freeway.

ISTR that trams in Leeds ran in the central reservation of the York Road

 

[Irascible]

Most of our motorways were built deliberately twisty ( in motorway terms ) in an attempt to keep us awake driving them, weren't they?

Perhaps we should do this properly & refund nature with an equivalent width of road for every new rail line.