I thought this concept of shoulder peaks was fairly common these days. Even in this tiny corner of Lancashire the service from Manchester Victoria steps up from a basic hourly to every 45 mins or so then to every half hour. Doesn't it make it easier operationally at major stations? It certainly means there isn't suddenly a massive rush of ECS runs to the depot all at once.
Northern actually seem to have removed a lot of what were shoulder peak services in favour of more strengthened standard pattern services.
The Mid-Cheshire line used to have:
15:0x Chester to Manchester - all stops (2 car 150)
15:4x Chester to Manchester - semi-fast (2 car 142)
16:0x Chester to Manchester - all stops (2 car 142)
It now has:
15:0x Chester to Manchester - all stops (4 car 150)
16:0x Chester to Manchester - all stops (2 car 142)
Also under First North Western we had something along the lines of:
09:0x Chester to Manchester - all stops
10: xx Northwich to Blackpool - semi-fast (Summer only)
10:0x Chester to Manchester - all stops
When Northern took over this became:
09:3x Northwich to Blackpool - stopper (north of Manchester this took the path previously taken by a Buxton-Manchester service)
10:0x Chester to Manchester - all stops
10: xx Manchester Piccadilly to Blackpool - semi-fast (Summer only)
And then got changed again in the Dec 08 timetable change.