Steve Beck and Paul Thomson make valid points about running diesel units on electrified track (Letters, PE May and June). However, the existing diesels still have a valid economic life left, which we should allow to run its course.
The extension of electrical power supplies to the whole network may be desirable, but it will not always be economic (witness the four trains a day from Edinburgh to Aberdeen), nor may it be practicable, particularly in regions where high wind and icing are more prevalent. So there will always be a place for trains that carry their own fuel supply for the whole journey.
But all new trains intended for service on existing partly electrified routes should have electric traction, particularly where plans for extending electrification are in place. We then bring back the tender in the form of a truck-mounted DG set, which can be hooked up to the electric train set at the last station before the wires stop and be uncoupled on the return journey.
Energy consumption should be reduced, because the diesel engines and fuel will be carried over shorter distances.
John Torrance, Flookburgh, Cumbria