Renewing Scotland’s trains

ScotRail currently operates 145 diesel and 203 electric trains, two thirds of which are approaching the end of their usable life. These operate InterCity services between Glasgow or Edinburgh to Aberdeen or Inverness, suburban services generally in Scotland’s central belt, and rural services including Scotland’s scenic routes.

In November, Transport Scotland published its fleet transition strategy explaining how ScotRail’s older trains are to be replaced. These are:

• Diesel High-Speed Trains (HSTs) built in the 1970s operating Inter-City services.
• Diesel Class 156 and 158 units serving suburban and rural services built in the late 1980s / early 1990s.
• Diesel single-car Class 153 units carrying cycles operating rural services built in the late 1980s.
• Electric Class 318 and 320 units operating suburban services built in the mid-1980s to 1990.
• Electric Class 334 units operating suburban services built between 1999 and 2002.

The strategy offers a flexible and financially sustainable approach to achieve the long-term aim of making Scotland’s railway net zero by 2045. It recognises the need to align infrastructure enhancement and train procurement in an uncertain and challenging financial environment. As shown below, it considers transitional, electric, battery-electric, and independently powered train fleets.

Transitional fleets

Being almost 50 years’ old, ScotRail’s oldest trains are its HSTs which are becoming increasingly expensive to maintain in a reliable condition and so soon need to be replaced. Although electrification is the preferred end-state for InterCity services, delivering this for HST fleet replacement would require high annual capital investment and cause significant service disruption.

Hence, in December 2024, Transport Scotland began the procurement to replace the HSTs by either younger lower-emission diesel trains cascaded from elsewhere in the UK or new bi-mode electro-diesel trains.

Electric trains

Electric trains – which are reliable, efficient, and cost less to build and maintain – and sufficient electrification is the preference for InterCity and the main Suburban passenger services. The strategy recognises that this also benefits freight and other services.

The strategy proposes the replacement of electric trains on the Glasgow inner suburban services, which carry 23% of ScotRail’s passengers. These are currently operated by three different classes of units which are typically over 35 years old. Replacing these with modern trains of a single class offers significant cost savings. In addition, the strategy proposes associated power supply upgrades.

There is currently no requirement to procure trains for longer distance suburban services which are operated by modern electric units, the Class 380s (built around 2009-11) and Class 385s (built 2015-19).

Battery-electric trains

The strategy recognises the rapid development of battery-trains which can be charged from the overhead line electrification system. Where there is no freight market, or as a transitional measure on InterCity routes, battery-electric trains deliver the same carbon benefits as an electric train with reduced capital investment.

Taking this into account, the plan is to replace diesel trains with battery electric trains on routes from Edinburgh to Tweedbank, Perth, and Dundee through Fife which carry 7% of ScotRail’s passengers.

Work has already started on the required discontinuous electrification in Fife for which a further £342 million funding, including the procurement of 69 trains, was announced in September.

The only feasible net zero carbon options to replace diesel trains on Scotland’s lengthy rural routes are battery-only or hydrogen trains. However, these are still commercially and technically immature and require further development. In the meantime, more modern Class 170 and Class 158 diesel units currently operating on the Fife and Borders routes will replace life-expired units operating on rural routes.

In the 20 years since Transport Scotland was established, Scotland’s rail passengers have benefited from a modernised network with a rolling electrification programme. This strategy is a pragmatic plan to continue to deliver better and more efficient services for Scotland’s rail passengers.

Image credit: David Shirres