"Boltar" wrote in message
oups.com...

Why would they haul it the whole way by loco? Wouldn't it be simpler
to take it to the limit of the 3rd rail (or 25KV if it also has a
pantograph) under its own power and then attach a loco and translator
vehicles to it?

No, it would be far more expensive. Firstly you would require two crews, one
with electric traction knowledge to take the unit to the limit of third rail
territory, then you would need a second crew with appropriate traction
knowledge to man the diesel locomotive, then you would need to take a
shunter with you to perform the coupling manoeuvre (rather than just leaving
him at his home depot - also, whilst he's out "on the road" he's
unproductive). For the marginal additional distance it is far cheaper to
take the diesel locomotive to the depot, get the depot staff to prepare the
train consist and then simply perform the move back to Derby. Running to
Brighton, rather than Clapham, is hardly significant extra mileage.