You pretty much never see a frequent and consistent local service (e.g 4TPH evenly spaced) on a two track line that also accomodates intercity or even regional express trains.How is this overcome in other areas of the country where this may still exist?
Many lines in and out of London are effectively 4 or even 6 tracks. Which helps keep the stoppers and the intercities out of each others way. The lines going round the edge of London don't really have any intercity traffic.
Merseyrails northern and wirral lines are essentially dedicated to mersyrail trains. The "city line" gets poor service because it's sharing with intercity and regional express trains.
It's possible to "flight" services, sending through trains of the same speed in succession. This improves train capacity, but it can also defeat the object of having a higher TPH. 2TPH evenly spaced is better than three trains at xx:2x, xx:3x, and xx:4x.
A combination of things.How do they manage to do this north of Preston with the stopping services and the expresses within many miles of two track railway- which is the post i was questioning?
Firstly they simply closed most of the stations between preston and carlisle, or in one case closed the mainline platforms and kept only those on the branch. Afaict there are only three stations left between preston and Carlisle.
Preston remains open.
Oxheys was closed in 1925
Barton and Broughton railway station was closed in 1965
Roebuck was closed in 1849
Garstang and Catterall was closed in 1969
Scorton was closed in 1939
Galgate was closed in 1939
Lancaster remains open.
Hest bank closed in 1969
Bolton le sands closed in 1969
Carnforth lost it's mainline platforms in 1970, it retains it's platforms on the branch.
Burton and Holme closed in 1966
Milnthorpe closed in 1968
Oxenholme remains open
Plumpton closed in 1948
Calthwaite closed in 1952
Southwaite closed in 1952
Wreay closed in 1943
Brisco closed in 1852
Carlisle is still open
Secondly, the services at some stations really aren't all that frequent. penrith for example gets an average of about two trains per hour southbound.
Thirdly, there appears to be "flighting" going on. If you look at the southbound timetable at penrith. there are frquently 40 plus minuite gaps and there is a 110 minuite gap between 19:48 and 21:39!.