With declining 165 reliability I thought the mk5s were replacing some 168s that might need to pick up 165 diagrams but Chiltern must be feeling confident.
Don't think i quite follow..
To be fair though the logic has been somewhat distorted.
Mk3s needed to go (overhaul time / major exams / age / cost - take your pick).
No mk3s = huge gap in capacity.
(Ageing 75 / 100 mph fleet adds to this issue)
Exercise undertaken to find additional capacity options.... mk5a successor to mk3 being this outcome.
Limited options available to reconfigure the fleet, take on enough to cover the loss of the mk3s only. ...All or nothing, so all it is.
Timetable rewrite required, and achieved, for dec26.
Mk5a now replaces most 100 mph units between London and Birmingham.
Timetable rewrite, naturally, forces stabling/ unit allocation / location issues.
With other factors involved (not mentionable here) the Timetable completely rejigged to reallocate capacity and units to alleviate other overcrowding pinch points.
It wasn't only Birmingham which has capacity constraints. Mk5a has both positive and negative aspects (see other threads) but it doesn't nessesarily follow that addition of mk5a sets means all the existing units will be reallocated as they just can't. It seems illogical, but this is the railway. Not much is as simple as may appear.
The short version would of course read:
All of Chilterns existing fleet is old and needs attention. The mk5a does not begin to solve all the issues faced, likely making some areas worse by reaction, while taking over important duties, everything else is rejigged behind them and may not fall back down in seemingly logical fashion.
