Infrastructure Work Etc required for New MU Speeds on WCML

[cambsy]

having looked through the Network Rail Sectional Appendix for WCMl South, it got me wandering what Infrastructure work has been required for the higher MU speeds, and what rules and regulations etc are followed for deciding how much faster than 110 mph can MU’s go? Have things like curve speeds and canting rules been changed to allow the higher MU speeds?

what got me thinking about all this, was the section through Cheddington, which although straight is still limited to 110 mph rather than say 125mph, which seems odd to me as at least heading South from Linslade Tunnels it’s straight beyond Leighton Buzzard, though going North there would be harsh braking down to the 90mph limit through Linslade Tunnels. Another thing is what will the ride be like at the higher speeds be like, as some of the higher speeds sections are not dead straight, and the 800’s are not best riding stock, so think the ride could be rough and interesting.

 

[Tilting007]

Only infrastructure changes are new signs.

The track work was done relating to the MU speeds.

Cheddington has MU in both directions, but where there are sites where it may seem there MU would be higher but are not due to drivability or restrictions either side being lower so it avoids having advance boards with AWS.

 

[Bald Rick]

and to add, there is no changes to curving rules. Albeit exceptional rates of cant deficiency are used more often than previously for non-tilt stock.

 

[AlexRail575]

what got me thinking about all this, was the section through Cheddington, which although straight is still limited to 110 mph rather than say 125mph, which seems odd to me as at least heading South from Linslade Tunnels it’s straight beyond Leighton Buzzard, though going North there would be harsh braking down to the 90mph limit through Linslade Tunnels. Another thing is what will the ride be like at the higher speeds be like, as some of the higher speeds sections are not dead straight, and the 800’s are not best riding stock, so think the ride could be rough and interesting.

It isn't that odd when you think about what else comes into play. Whether the track is straight or not is far from being the sole factor in figuring out what the speed limit may be for a section of track. Higher speed lines also require significant investment in the underlying infrastracture as well as more maintenance cost to ensure track stays within tolerances &c

Signal spacing also matters - higher speeds are only possible where the trains are able to come to a stand within the available braking distance from the signalling system (whether it be lineside or cab signalling); otherwise in addition to the higher track maintenance costs you're also going to have to adjust the layout of signals, in itself an expensive exercise, before one starts considering possible impacts on line capacity.

As a side note, the opposite end of the scale is that, if you're really willing to spare on maintenance costs, you can probably run any train on any track if you keep a low enough speed - if you want to see how some North American railways do their business, look below. In that particular case the "passengers" don't tend to complain about the ride quality (or the journey time), though...

 

[plugwash]

whether it be lineside or cab signalling

AIUI the big difference between lineside signalling and ETCS is that with lineside signalling you essentially have to signal pessimistically based on the worst-case combination of speed and braking power that is allowed on the line. If you increase speeds then you face having to either move signals further apart, or introduce non-standard aspect sequences.

Whereas with ETCS, increasing the maximum speed just means you have to "look ahead" further when assigning movement authorities. You can still keep the existing block positions and you can still assign movement authorities that are "no worse" than the ones you assigned before the max speed change.

 

[edwin_m]

The reason the WCML hasn't had faster MU speeds until now is basically because nobody has asked and been willing to pay to have it assessed. Virgin only wanted to run tilting trains so only wanted the WCML upgrade to improve EPSs - any benefit to other trains might have helped a competitor.

 

[AlexRail575]

AIUI the big difference between lineside signalling and ETCS is that with lineside signalling you essentially have to signal pessimistically based on the worst-case combination of speed and braking power that is allowed on the line. If you increase speeds then you face having to either move signals further apart, or introduce non-standard aspect sequences.

Whereas with ETCS, increasing the maximum speed just means you have to "look ahead" further when assigning movement authorities. You can still keep the existing block positions and you can still assign movement authorities that are "no worse" than the ones you assigned before the max speed change.

Cab signalling systems (this probably applies to most of the vast array of national varieties of cab signalling, ETCS as you point out might be more advanced in this regard, I'm not exactly too knowledgeable about the technical details) are indeed more flexible, but not all can enforce any arbitrary speed limit or braking curve, and if a line isn't already equipped with such then that in itself is already a significant investment and if capacity is scarce and the line speed already high, increasing the linespeed by a relatively marginal amount (the "look ahead" distance increasing of course by a much larger margin) might not necessarily be advantageous.