TfL plans replacement programme for ageing battery locomotive fleet

Transport for London (TfL) is preparing to replace its fleet of battery-powered engineering locomotives, some of which contain components dating back more than a century.

The specialised locomotives, used to haul engineering and maintenance trains across the London Underground network, have been a vital part of TfL’s infrastructure operations for decades. Originally converted from London Underground passenger stock built in the 1920s, the vehicles were repurposed during the 1960s and continue to use elements of their original traction equipment.

TfL currently operates a fleet of 29 battery locomotives, but increasing maintenance requirements, ageing systems and operational limitations have prompted plans for a full replacement programme.

While the cost of the new fleet has not been publicly disclosed, the procurement is understood to represent an investment running into hundreds of millions of pounds.

Ian Rawlings, TfL’s Head of Profession for Vehicle Engineering, said the existing fleet remains essential but is becoming increasingly difficult and expensive to maintain.

“They are quite expensive to maintain, not the most reliable and don’t have the nicest working environments for those on them or for people maintaining them,” he said.

The locomotives lack many of the features expected in modern rolling stock, with cramped driver cabs, no air conditioning and ageing mechanical systems. Their heritage design also means specialist maintenance skills are increasingly difficult to source, including traditional techniques such as hot riveting used on the vehicles’ bogies.

Reliability challenges have become more pronounced as the fleet has aged, resulting in greater maintenance demands to keep the locomotives operational.

The vehicles play a critical role in supporting overnight engineering works and infrastructure renewals across the Underground network. TfL requires at least 14 locomotives to be available at any one time to support maintenance programmes.

The replacement fleet will be designed to operate in pairs, hauling engineering trains up to 139 metres in length and weighing as much as 600 tonnes.

New locomotives will need to be compatible with multiple signalling systems across the Underground network and operate on most lines, although they will not be required for use on the Victoria or Waterloo & City lines.

In a preliminary market engagement exercise, TfL described the future fleet as "critical" to maintaining and improving the Underground's infrastructure, highlighting the need for improved reliability, operational efficiency and zero-emission technology.

Rawlings said the project has already generated international interest from manufacturers.

“We have had interest from manufacturers across the globe,” he said.

However, he acknowledged that the procurement presents unique challenges due to the bespoke nature of the vehicles required.

“It’s a challenge for us, because of the need for bespoke-gauge locomotives, there’s no existing off-the-shelf product.”

He added:

“It’s not one or two. It’s not mass production, it sits in a difficult niche in the middle.”

TfL currently intends to appoint a preferred manufacturer by 2029, allowing design work to begin before production gets underway. Delivery of the new fleet is expected during the 2030s.

The project represents one of the most significant investments in TfL’s engineering fleet for many years and will ensure the Underground has the specialist equipment needed to support maintenance, renewals and infrastructure upgrades well into the future.