A Strategic Business Case for partial electrification of the Chiltern Main Line has been compiled.
Discontinuous electrification of the route and new battery-electric trains from part of phase three of Chiltern Railways' 2030 Vision.
This will follow the refurbishment of Class 168
diesel multiple units and the introduction of Mk 5A carriages on services between London Marylebone and Birmingham. Marylebone is the only London terminus to not be electrified.
Speaking at the Mk 5A launch event, Chiltern Managing Director Richard Allan said precise locations had not been finalised, but noted: "We think Marylebone station, north of High Wycombe, and then wiring potentially towards Oxford or Banbury, and then look at new trains, infrastructure and power supply.
"We've done the Strategic Business Case. We now need to move to the Outline Business Case. As part of that, we want to go and talk to train manufacturers and say: 'can you provide a price for a package for power supply, infrastructure and trains to achieve an outcome that we will specify'." Electrification south from Snow Hill is also a possibility.
Reiterating that final locations are yet to be decided, Allan added that "relatively small" amounts of electrification would be enough to bring in battery-electric trains. Chiltern, Network Rail and the Department for Transport have agreed on discontinuous electrification, with work to understand what the market can provide, and the cost and benefits analysis still needing to be done.
Explaining why electrifying the entire 120-mile route was unlikely, Allan said: "You imagine putting wires through the tunnels at Marylebone. Very expensive, very disruptive."
He said the outcomes from that consultation will inform the final business case, which will include assessments of the cost, noise benefits, revenue benefit, and emissions.
While no specific timescale has been put in place, Allan said he'd like it to happen
"as soon as we can".
He added: "The trains we want to replace are the 165' diesels. They are 34 years old. The work may take five years from start to finish, from business case, conclusion and introduction into traffic." Allan said the Class 165s are still reliable, but maintain 3+2 seating and are showing their age.
"It's getting more challenging to find parts. We have people who have worked all their lives on the '165s', and know them inside and out. But they will get to 40 years and beyond. We have to be urgently looking now at their replacement. "And the replacement cannot be diesel. It cannot be like-for-like. It has to be a new technology and something that allows Chiltern trains to go from being an old diesel to being greener and quieter." Speaking about the Mk 5As, Allan said CR spent 18 months on the business case and had been talking to owners of various options to replace its Mk 3s. He told RAIL the operator had made the case for phase two of the 2030 Vision so it could increase services.
The Mk 5As will be used for the majority of Birmingham services, allowing Class 168s to be primarily used on Chiltern's Oxford route and the older '165s' to be primarily used on shorter routes to places such as Aylesbury and High Wycombe. At present '168s' are still used regularly on the Birmingham route, with Class 165s required to run to Oxford at times.
"We run around 350 services a weekday. We will take that to around 375-380 from December 2026. That's principally filling in the gaps, said Allan.
Examples of gaps include periods of the day when the Birmingham service is hourly instead of half-hourly.
Mk 5As will also be used for relief services in peak hours, mainly between Banbury and Marylebone.
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