Fantasy: Bristol Parkway Grade Separation

[Topological]

Not one I have seen before, so this is a thought I have had when using Bristol Parkway.

The stages are basically:

1. Add a new island to the south of the existing pair. This island to be built wider than the existing islands and ideally far enough to allow the current platform 1 to be extended southwards to widen the island there too.
2. Once the new island is in use work can begin to widen the 1 and 2 island. For this time Cardiff bound trains use 3 and trains from Cardiff use 4.
3. Work should then begin to widen the line Eastwards so that a grade-separated flyover can bring Eastbound trains from Bristol over to the north side of the formation.
4. Finally, the junction at Westerleigh would be grade separated so that there was no conflict between trains arriving from Birmingham and trains going towards Swindon.

IF the plans allow a station could be added at Winterbourne, but that might need some compulsory purchase to have 4 tracks between Parkway and Winterbourne station.

Ultimately Bristol Parkway would end up with 6 platforms, be an easier place to terminate local services from Bristol and less of a conflict for long distance services. The wider islands would make connecting more comfortable as well. The grade separation elements would allow more local services up towards Gloucester without pathing conflicts on the GWML.

A lot of money and total fantasy, but why not?

 

[Meerkat]

My crayons have often stared at the map and tried to find a route for a new line from Yate to the southside of Parkway, but it would probably involve a couple of tunnels and major engineering so ££££.
First question…is there actually a problem with conflicts at Westerleigh and Parkway?
If so would grade separating Westerleigh be solution enough?

 

[FGWHST43009]

My crayons have often stared at the map and tried to find a route for a new line from Yate to the southside of Parkway, but it would probably involve a couple of tunnels and major engineering so ££££.
First question…is there actually a problem with conflicts at Westerleigh and Parkway?
If so would grade separating Westerleigh be solution enough?

I think any rebuilding of the junction should include an increase in diverging speeds. If trains could diverge at say, 75-90mph that would be better than 55mph currently. Of course this would cost more but could reduce journey times albeit not by much but also ease a known constraint

 

[The Planner]

First question…is there actually a problem with conflicts at Westerleigh and Parkway?
If so would grade separating Westerleigh be solution enough?

Its often been looked at.

 

[Meerkat]

Its often been looked at.

What were the answers - is there really a problem to fix?

 

[brad465]

I think any rebuilding of the junction should include an increase in diverging speeds. If trains could diverge at say, 75-90mph that would be better than 55mph currently. Of course this would cost more but could reduce journey times albeit not by much but also ease a known constraint

I thought it was 40mph at the jct itself, rising to 55mph just beyond it towards Yate, then 65mph soon after, before 90+mph by the jct with the freight line.

If grade separation and remodelling was going to be pursued, I think it would make sense to make a new northbound link join up with the freight line without going over it, to provide a smoother curve (the land only appears to be farmland if you can avoid the solar farm). The existing curve could remain for Bristol-bound trains, but reusing the alignment to pass underneath the South Wales Mainline then rise to join it. This would require a long possession though if the alignment was going to be identical.

 

[The Planner]

What were the answers - is there really a problem to fix?

The fact that nothing has ever happened should tell you. However if for whatever reason a propsed increase in services on the GWML and XC route occured, it might start getting challenging.

 

[Topological]

My fantasy based solution was to untangle all of the junctions, motivated by the opportunity to add local trains to Bristol as well. How much capacity is there for Bristol to introduce a metro type service between Temple Meads, Parkway and perhaps further North/East?

Though it now occurs to me there would probably be more interest in a tram like operation that ran through UWE and into the city rather than Temple Meads. Such a line could interact with Parkway without moving any of the heavy rail (it could also get to the Yate line as well in theory)

 

[Meerkat]

The fact that nothing has ever happened should tell you. However if for whatever reason a propsed increase in services on the GWML and XC route occured, it might start getting challenging.

Not really - it could just mean that the problem was not big enough/the cost was too big to do anything about it, or just that it was a problem but not a high enough priority to get a share of the limited railway funding.
I am just curious whether it is causing noticeable performance issues and or major timetable constraints.

 

[Pat31]

Not really - it could just mean that the problem was not big enough/the cost was too big to do anything about it, or just that it was a problem but not a high enough priority to get a share of the limited railway funding.
I am just curious whether it is causing noticeable performance issues and or major timetable constraints.

I don't think it causes many issues at the moment, occasional waiting for trains that have conflicting movements but in my mind it doesn't cause congestion bad enough to warrant grade separation. Increased services to Gloucester and beyond either from GW or XC can't really be facilitated as the junction is more or less at capacity. I have seen this idea banded about before.

 

[The exile]

As a regular (lay) user I would judge that, as things stand, the west end of Parkway just about copes, but there’s little wriggle room when things start to go wrong or for any service enhancement. (For example reinstating the ability to get direct between Stapleton Road / Lawrence Hill/Ashley Down and Parkway). A very beneficial side effect of grade separation at the west end would be the inevitable rebuilding of the road bridge - removing a massive bottleneck.

 

[AndrewE]

I don't think it causes many issues at the moment, occasional waiting for trains that have conflicting movements but in my mind it doesn't cause congestion bad enough to warrant grade separation. Increased services to Gloucester and beyond either from GW or XC can't really be facilitated as the junction is more or less at capacity. I have seen this idea banded about before.

aren't you disagreeing with yourself there? No problems currently but we can't improve NE-SW services because there is no capacity...

 

[The exile]

aren't you disagreeing with yourself there? No problems currently but we can't improve NE-SW services because there is no capacity...

Those two statements aren’t a contradiction. The layout copes now, but try to add more trains in and it probably wouldn’t. Not saying this is a correct analysis of the current situation - merely that both statements can be true simultaneously.

 

[Pat31]

aren't you disagreeing with yourself there? No problems currently but we can't improve NE-SW services because there is no capacity...

I don't think so, I think @The exile summed it up nicely. Currently not causing many issues but add more services in and you might have more significant congestion potentially? I'm not well informed here just going off own opinion from what I've seen posted before and read.

 

[Dr Day]

Cross Country and some GWR services should be longer but is frequency that much of a problem on this axis?

 

[MarkyT]

The fact that nothing has ever happened should tell you. However if for whatever reason a propsed increase in services on the GWML and XC route occured, it might start getting challenging.

The low turnout speed doesn't impact journey times much as modern trains can accelerate out of the restriction quickly. The occupancy time through the junction is probably a more important factor. As the slowest movements across the junction, longer and more frequent XCs particularly, and additional Gloucester line stoppers and freights would increase conflict with the Swindon bound Up Main significantly. Turnout and curve speed improvement would help a little, hurrying along those conflicting movements. My suggestion would be an approx 1000m (~75-80mph) radius curve as shown yellow. That would be the base scheme, retaining a faster but still flat junction with GWML (double ladder form with 75mph turnouts). An enhancement, constructed at the same time or as a later upgrade, would be the single track Up Main diversion in blue to avoid the flat junction. This, dropping to ground level in fields at the intersection, would pass under the new Gloucester alignment which launches from the existing GW embankment nearby. If the fly-under enhancement was to be constructed later then land safeguarding and the intersection bridge to be provided in the earlier scheme.