m8internet wrote:Fleets need to be flexible, which locos and coaches are not.
This is a rail industry half-truth that has had currency since Beeching's day. In some respects MUs are flexible, but in others they are not.
It is true that MUs can often carry-on in service even with one failed power car, whereas a failed loco is (except for double-headers and top-and-tail) a failed train.
However, other claims as to the superiority of MUs are much more questionable. A few examples:
Track wear and tear - The axle load of a loco is greater than an MU car, but the modern practice of all powered MU cars means the axle load of MU cars is greater than that of hauled stock. And, of course, the damage done to track by 'Pacers' is legendary!
Flexibility to meet passenger demand - While the theory may be sound, all too often the delivery of 2-car and/or 3-car units has frequently resulted in the operation of trains of just that length - regardless of peak demands.
Inter-city MUs - These are generally quite inflexible. The Pendolinos are a classic example of inflexibility. A loco and hauled stock could be formed of loco + 7 at quiet times and loco + 14 at peaks. With Pendolinos it's either 9-cars or no train! A waste of energy and resources in the late evenings and wholly inadequate in the peaks. Where's the flexibility in that?