wrote
John Salmon wrote:
Merseyrail isn't a good example of how it should be done. The
entire electrified system including the loop and link lines were
designed for six-car operation, then after a very short time the
trains were reduced to three cars - which is why SET and LO ended
up with Class 508 units.

That's all very well but the 508s were built (as 4 car units) for what is
now SWT. One car from each 508 went into a 455 unit. Only then were the
508s sent to Merseyside.

True, *all* the 3-car 508s went north but then several of them came back
south again, after the six-car trains were reduced to three-car. So I'm not
clear what point you're making.