3rd rail infills and extensions may have a future after all…

[A0wen]

To an extent but bear in mind that in terms of efficiency a bimode is a dmu lugging around an electric motor. Simultaneously it is an emu burdened with a fuel tank and diesel engine. It is the short term thinkers pseudo solution to avoid electrification.

Not necessarily - a bi-mode could be battery / electric with the battery being charged when the unit is operating from OHL / 3rd rail.

I fail to see why looking at bi-modes is wrong, when there are *significant* costs to electrify the rail network - the electrification of the Midland Mainline from Market Harborough to Sheffield is estimated to cost £ 500m - for ~ 100 miles of electrification - that's £ 5m / mile and assumes things like connection to the National Grid are readily available etc. For many lines discontinuous electrification with bi-modes makes far more sense, both practically and economically.

 

[Irascible]

Regardless of any extensions, there's going to be a lot of existing 3rd rail around for the foreseeable future as widespread conversion to OHLE seems unlikely. Safety improvements for both staff and public cannot be ignored in this large network going forward. More finely grained remote-controlled isolation facilities would be a good start, allowing isolations to be a default for all routine on-track maintenance activities. What could make this practical is for all DC electric trains to have a moderately sized traction battery on board that could carry them through short isolations with no significant loss of performance. While some units might carry much larger batteries for longer off-grid excursions, a (say) 10-mile battery range for all units could be very useful to cover planned and unplanned local outages, and shunt around depots, where conductor rails could normally be left isolated, except when trains are being charged stationary overnight in stabling sidings. Such a battery could be small and light enough to accommodate somewhere even on existing vehicles.

3rd rail units need batteries full stop - smooths off all that peak power draw & might finally get them performing like they would on AC. You might even manage to reduce infrastructure a bit if you can go discontinuous electrification in places.

 

[MarkyT]

3rd rail units need batteries full stop - smooths off all that peak power draw & might finally get them performing like they would on AC. You might even manage to reduce infrastructure a bit if you can go discontinuous electrification in places.

Indeed, and batteries could capture some regen brake energy even when the local substation isn't receptive. Trains could also cope with longer gaps through junctions, reducing the number of individual conductor rail sections required, and the quantity of connecting cables between them in such complex areas.

 

[The Ham]

Indeed, and batteries could capture some regen brake energy even when the local substation isn't receptive. Trains could also cope with longer gaps through junctions, reducing the number of individual conductor rail sections required, and the quantity of connecting cables between them in such complex areas.

Presumably it could also help with the complexities where there's a chance from DC to AC.

 

[zwk500]

Presumably it could also help with the complexities where there's a chance from DC to AC.

It would help immensely as you'd be able to essentially have 2 completely separate sections with the battery bridging the gap between them. Batteries would also help during incidents where the power is shut off, as trains would be able to move forward to the next platform, giving passengers the opportunity to at least get off the train.

 

[Irascible]

Indeed, and batteries could capture some regen brake energy even when the local substation isn't receptive. Trains could also cope with longer gaps through junctions, reducing the number of individual conductor rail sections required, and the quantity of connecting cables between them in such complex areas.

There's no particular reason a train couldn't discharge it's batteries into the rail if the local power supply asked for it, either. If it's just sitting around & the substation is struggling to supply everything else going on, why not.

Admittedly I'd rather batteries were used to remove 3rd rail from platform areas, but trains do stop outside platforms every now and then!

 

[Chrisgr31]

This is yet another thread on the subject, and must be the most amusing to date given the quantity of frothing. NR have been talking to ORR about this for at least 3 years, why it has suddenly appeared in RAIL is beyond me.

the reason is potentially linked to this https://www.rssb.co.uk/search#search-results_e=0&search-results_q=T1214 which I was told in March would be published in around a month.

That is tail wagging dog territory. Uckfield trains have to be a certain length to accommodate passengers at Hurst Green, Oxted and East Croydon who board them as if they were any other service.

Who is to say that an East Grinstead fast using electric stock and the Uckfield path into London and removing what is left of Thameslink on the East Grinstead line wouldn't be a greener way to use the path, with passengers for Uckfield changing at Oxted?

Then fewer bespoke battery units are needed.

Because passengers changing at Oxted are likely to vote with their feet and not travel at all! I can remember the days of changing at Oxted and it was a pain in the bum. It means you can’t sleep on the journey, it provides risks of not getting a seat from Oxted, it creates the risk of getting stuck at Oxted if the shuttle is cancelled, it also means potentially a 6 carriage full train disgorging on to a busy platform, it increases the journey time.