The Anonymous Widower

What Happened To The Class 158/159 Bi-Mode Study?

In Class 158/159 Bi-Modes?, I discussed the possibility of turning South Western Railway‘s Class 158 and Class 159 trains into bi-modes.

I said this.

In the March 2018 Edition of Modern Railways, there is a short news item, which is entitled Bi-Mode Study For SWR DMUs.

The Class 158 and Class 159 diesel multiple units used by South Western Railway are diesel-hydraulic units.

Under their franchise agreement, South Western Railway, agreed to perform a study, to see if the multiple units could be converted from diesel-hydraulic to diesel-electric transmission.

If this is successful, then the plan would be to fit a third-rail capability to the trains, so they could use the electrification between Basingstoke and Waterloo on services to Salisbury and Exeter.

Could the conversion also raise the operating speed of the trains from their current 90 mph to a more timetable-friendly 100 mph?

It looks like it could be a feasible , especially as the article states they might re-use redundant modern traction equipment from Class 455 trains, which are due for replacement.

It sounded a sensible plan to do a study.

But we’ve heard nothing since.

  • Has the late delivery of the Class 701 trains, pushed the availability of the Class 455 trains, that wioll donate the traction system, too far into the future?
  • Has the Covids delayed another project?
  • Would First Group prefer more Hitachi trains as five of their companies use them or have them on order?
  • Is the 90 mph speed of the diesel trains, too slow for the busy London Waterloo and Basingstoke route?

Or could it be that Alstom, CAF, Hitachi, Stadler or another manufacturer have a much better zero-carbon plan?

September 13, 2021 - Posted by | Transport/Travel | , , ,


  1. Perhaps there reworking it with the traction equipment thats been stripped from the 442’s?

    This is a short term fudge reliable though these DMUs are they are getting old and my take is they should electrify Reading to Basingstoke and down to Salisbury/Romsey at 25kv. This would give a freight route as well as passenger train opportunities. Azumas if they can sort the fatigue issues can easily be fitted with shoegear and modern traction inverters can run on 750V DC direct with minimal additional kit as well as 25kv when thats available. Then the decision has to be is it diesels or batteries with fast charging at stations probably from short O/H sections which can be connected to the local DNO using SFCs.

    Comment by Nicholas Lewis | September 13, 2021 | Reply

  2. I suspect that they’ve had a better solution offered by Alstom, CAF, Hitachi or Stadler. Or more likely four better solutions.

    Alstom could be offering hydrogen Class 600 trains. But I do wonder if hydrogen has gone off the boil for passenger trains.

    CAF could probably offer Class 331 trains with batteries.

    Hitachi could be offering Class 385 trains or Class 802 trains with batteries. Either would fit, but the spec would be similar to what ScotRail will probably order for Glasgow’s proposed battery electric services.

    Stadler could offer Class 755 trains with batteries.

    My money’s on the Swiss, as they are on a roll!

    Remember too, that SWR are run by First Group, who own Lumo and that service uses Hitachi trains with batteries, for emergency purposes, when the wires come down.

    Comment by AnonW | September 13, 2021 | Reply

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