Presumably the use of 8-car 360 units off-peak has the benefit of lower track access charges during the day as opposed to operating 12-car throughout the day.
But this would require the removal of 4-car units as ECS to somewhere like Cricklewood for stabling until they return to St Pancras for the evening peak.
I'm interested to know whether the additional ECS movements and daily splitting/rejoining would really save any costs. It might be just as efficient to use 12-car all day and balance the additional operating costs versus ECS and stabling costs.
Perhaps someone knows ?
Track access charges are fairly low, generally the reason for shorter services is to balance the maintenance costs and/or the lease costs.
However if the RSOCO wood otherwise be left with a micro fleet they may offer the extra units for a fairly nominal amount, say 18 units for £1 million with the extra 3 units costing an extra £1,000.
It being such a small amount that the TOC think we'll we might as well, but it saves the RSOCO a load of costs with having them sat idle and no scope to find another home.
Indeed it could even be that there's a reduction in costs to have the whole fleet, say £130,000 per coach or £100,000 pet coach if you take the whole fleet, meaning that it's cheaper to have 21 units than 17 and only slightly more than 16.