Or, as in a similar case where I was once told by an EMT director in the early days of their franchise, "15886x is the most reliable in the fleet: it never fails. It's also never been off Eastcroft depot since it transferred to us!"
Is that not at least in part due to the engineering works overrunning on the line?
I know we can twist the figures various ways, but the number of delayed/cancelled cars and services, car miles planned and car miles lost, is exactly the same. Although the fault may be on the "other" unit, both have the delay. The number of faults where the train is split up and the second unit carries on (and to time!) is pretty small.
But a 700 has a far higher capacity than a 4-car unit, so the following train would better clear the additional passengers. In many cases, (and especially in the TL core) recovery of failed units in a conventional consist of 4-car units could be difficult with adverse 1:29 gradients out of the section.
A 700 doesn't need splitting, - a unit with one half inoperative is capable of pushing a whole failed unit up the gradients with minimal delays.
I'm afraid that's statistical nonsense. You're claiming that if a given half-unit failed at 20'000 miles, the other half would've continued another 20'000 miles to fail at the 40'000 miles MTIN - but that's statistically improbable - the counter doesn't reset just because one half failed. You also seem to assume all issues are due to uncorrelated hardware issues in a half-unit - but what about all the failures caused by external issues that would affect both units (examples include some power fluctuation that knocks out a pair of units together but in just one location). You'd need to look at the distribution of failures to come up with a realistic estimate of the new MTIN, and doubling it is not the answer.
The coupling between the two halves of a 700 is only ever operated in a depot, unlike normal MUs that can be split several times a week in service. On that basis a coupling failure in service is extremely unlikely. Even a total power failure in service on one half unit wouldn't normally stop the other half dragging the consist clear.
Fair point
So how would the class 700s fare when the ac power dipped out of spec causing them to fail safe. The whole MML south was blocked, more because there weren't enough support staff to reboot the on-board system than the fact that they tripped in the first instance.
