Bi-mode trains: Unlocking opportunity? (Rail Engineer)

“The future is bright, the future is bi-mode!” or so one might imagine with the level of focus on this type of train. There are a number of bi-mode trains being developed or manufactured and the Government sees them as a way of bringing forward the passenger benefits planned to be delivered through the authorised electrification programmes, several of which are now running significantly both late and over budget.

More recently, the planned electrification from Kettering to Nottingham and Sheffield has been cancelled in favour of modern bi-mode trains that are supposed to deliver, for example, a 20-minute reduction in journey time between Sheffield and London. Expecting the train in diesel mode to deliver this time saving will be a serious technical challenge and, in fact, it is rumoured that the saving is to be achieved solely by infrastructure changes and by omitting stops south of Leicester. This article will show that bi-mode trains in self-powered mode will struggle to deliver anything like the performance possible in electric mode

Background

It was around 2005 that the Department for Transport (DfT) was considering the specification of a train to replace the diesel High Speed Train (HST). Some of the routes where the new train was planned to operate were electrified, at least on the trunk sections, and it was desirable to make use of this infrastructure. However, the DfT also recognised that passengers valued the through journeys they enjoyed to destinations beyond the electrified network using HSTs, for example London to Aberdeen, and thus a number of options to maintain such services were considered:

1. New diesel trains equivalent to the HST;
2. Electric trains taken beyond the electrified network by diesel locomotives (as per the original Bournemouth electrification, and early days of Pendolinos from Crewe to Chester/Holyhead);
3. Provide electric trains that have a self-propulsion capability – which came to be known as bi-mode trains;
4. Making passengers change trains.

As is well known, DfT selected option 3 and, despite many commentators’ contrary views, this was probably the only sensible option for passenger services that run on both electrified and non-electrified routes.

Whether bi-mode technology justifies the cancellation schemes is another matter. However, bi-modes do bring additional benefits other than just using non-electrified routes, such as accessing secondary platform faces, depots, stabling sidings and diversionary routes.

Since then, Abellio Greater Anglia has ordered bi-mode trains and there are prototypes under development for more.

This article describes the benefits and challenges of bi-modes and provides a roundup of current bi-mode trains under construction and in development. It assumes the following:

• Bi-mode trains are electric trains with the means to move independently of the electrification infrastructure;
• Even if it is carried out at a reasonable cost, there will never be a business case to electrify the whole railway;
• Rolling stock programmes and infrastructure programmes can never be fully aligned;
• Bi-mode trains in self-powered mode incur performance and/or range penalties compared with operation from the electricity supply.

Rest of article