Colton junction : "first 125mph points" in the UK

[Justin Smith]

Could the esteemed members of this forum explain something to me ?
When the Selby diversion was built much was made about the 125mph points at Colton junction.
But surely the points at Hambleton and Temple Hirst must also be 125mph ?
Or, for them to classed as 125mph points, does the 125mph have to be for the turnout, i.e. if the straight ahead is 125mph but the turnout is not they are not classed as 125mph ?

 

[LNW-GW Joint]

It will be because both routes at Colton are signed for 125mph - with the Doncaster (ECML) route actually being the divergent one.
There are many places where 125 is allowed on the straight route but a lower speed on the diverging route.

The curiosity at Colton is that, while both routes at the junction (towards Doncaster and Normanton) are 125mph, the Normanton route reduces to 100mph in a mile and then 80mph in another mile, so is rather pointless (sorry!).
In the Down direction the Normanton is 100 right up to the junction.
I think the Leeds lines will also go to 125mph when the TRU electrification is complete at Colton.

For a purposeful 125mph in both directions at a junction, go to Rugby Trent Valley Jn, where both the Trent Valley and Coventry lines are 125mph in the Down direction (for Pendolinos).
HSL's often have junctions/crossovers rated at 140mph or higher, spread out over long linear distances.

 

[edwin_m]

What is commonly described as a "xxmph point" is better referred to as a "xxmph turnout", as the speed of the curved route is being referred to and there is no particular restriction on the straight route. Having said that, I believe the points at Colton are symmetrical so both routes are equally curved at a radius that allows 125mph but perhaps no faster.

When Temple Hirst junction was created, the tracks were re-aligned so the formerly straight route via Selby became connected via a turnout and crossover, and the straight tracks through the junction becoming to/from the diversion.

HSL's often have junctions/crossovers rated at 140mph or higher, spread out over long linear distances.

As of a couple of years ago, 140mph or the metric equivalent was the fastest turnout that suppliers produced.

 

[ac6000cw]

Minor point related to the thread title, but I think the first set of points designed for a 125mph turnout speed were the prototype set BR installed at Soham (at the single to double track junction) for development/reliability testing - at rather lower speeds - before the design was used at Colton.

There was a related thread a few years ago - https://www.railforums.co.uk/thread...-the-uk-for-facing-points-line-change.221982/

 

[adamedwards]

Back in the 1980s, BR planned to upgrade the Normanton route as a higher speed line for Cross Country from York direct to Sheffield, hence the 125mph speeds on both routes. However, the InterCity sector realised that it made no sense to miss out Leeds or Doncaster and so this upgrade was abandonned in favour of works at Doncaster to make the route from there to Sheffield via Swinton and the route from Sheffield to Wakefield Westgate into higher speed routes instead, in particular using differential speeds as the HSTs could run at higher speeds as lower axle loads and brake more rapidly than loco hauled stock,. There were quite major junction and rationalisation works around Swinton and at Mexborough, if I remember rightly.

Part of the rationale of the changes was these two routes shared with the ECML and so shared costs were reduced costs, but also that more coal mines planned would mean the Normantion route would suffer subsidence.

 

[Purple Train]

Just thinking out loud here: were HS2 to be built (!!) and to 250mph, how long would a hypothetical 250mph turnout be?

 

[Justin Smith]

Back in the 1980s, BR planned to upgrade the Normanton route as a higher speed line for Cross Country from York direct to Sheffield, hence the 125mph speeds on both routes. However, the InterCity sector realised that it made no sense to miss out Leeds or Doncaster and so this upgrade was abandonned in favour of works at Doncaster to make the route from there to Sheffield via Swinton and the route from Sheffield to Wakefield Westgate into higher speed routes instead, in particular using differential speeds as the HSTs could run at higher speeds as lower axle loads and brake more rapidly than loco hauled stock,. There were quite major junction and rationalisation works around Swinton and at Mexborough, if I remember rightly.

That possibly explains why they did not use the ECML as the through route with the Leeds route diverging off it. Though, it appears, that, in the end, the much vaunted 125mph points were a bit of a waste of money really....

 

[Lucan]

The curiosity at Colton is that, while both routes at the junction (towards Doncaster and Normanton) are 125mph, the Normanton route reduces to 100mph in a mile and then 80mph in another mile, so is rather pointless (sorry!).

If trains had to slow to 100mph or 80mph before the points they would be occupying that part of the track for longer and so reducing the capacity of the Doncaster route, even though it would make little difference to that of the Normanton route.

 

[Taunton]

Back in the 1980s, BR planned to upgrade the Normanton route as a higher speed line for Cross Country from York direct to Sheffield, hence the 125mph speeds on both routes. However, the InterCity sector realised that it made no sense to miss out Leeds or Doncaster and so this upgrade was abandonned in favour of works at Doncaster to make the route from there to Sheffield via Swinton and the route from Sheffield to Wakefield Westgate into higher speed routes instead, in particular using differential speeds as the HSTs could run at higher speeds as lower axle loads and brake more rapidly than loco hauled stock,. There were quite major junction and rationalisation works around Swinton and at Mexborough, if I remember rightly.

There were a series of projects, and changes of mind, in the 1970s-80s for how to route mainstream North-East to South-West services between Sheffield to York, which had traditionally served neither Leeds nor Doncaster, and the routing went back and forth. Mining subsidence alleviation was part of it, but there did seem to be much investment which was not particularly used, and indeed some routes fettled up then to modern standards are now abandoned.

 

[LNW-GW Joint]

If trains had to slow to 100mph or 80mph before the points they would be occupying that part of the track for longer and so reducing the capacity of the Doncaster route, even though it would make little difference to that of the Normanton route.

Well, how many 125mph trains take the Normanton route out of York?
All the fast services (apart from the ECML) head for Leeds on the other tracks.
Normanton is normally freight and diversions, though TPE will be using the route more during TRU works.

 

[HurdyGurdy]

Though, it appears, that, in the end, the much vaunted 125mph points were a bit of a waste of money really....

That's not necessarily the case. At Colton, a through alignment could have been designed for the route to Doncaster, with a curve would have permitted 125mph. But a double junction towards the Normanton route, even using the same long switches and crossings as the current junction, placed on that curve would not necessarily permit even 80mph.

To get round that, a higher speed on the Normanton route was achieved by slewing it to create a reverse curve. The junction was placed on the part of that curve which is curving in the opposite sense to the Doncaster route. It's a split turnout arrangement, where neither is a through route, they diverge from each other. Doing it that way and having a symmetrical split, the 125mph towards Normanton almost comes as a free gift.