Terminus Station Approach

[BluenGreyAnorak]

I found a diagram of Bournemouth West on www.signalbox.org. Interestingly, it has a double slip on the running line, two scissors and no loco release crossovers. Looks like an ideal prototype

Excellent. What's that saying about a prototype for everything?

[The Stationmaster]

Excellent. What's that saying about a prototype for everything?

 

Yes - but don't forget that layout at Bournemouth West is very much a child of the steam era. From the mid '60s onwards (to some extent depending on Regional views) the nature of British track layouts began to change dramatically with rationalisation creeping ever more to the fore.

[BluenGreyAnorak]

Yeah, of course. What sort of alterations did rationalisation involve though? Were they driven primarily by changes in traffic levels or mainly by changes from steam to diesel haulage? Assuming, for example, a location where traffic levels didn't change significantly, would track changes likely only include the removal of steam engine turning and servicing facilties, or were there other factors?

 

Or is that an unlikely scenario? Did traffic levels change to such an extent during that period that it all went hand in hand?

[Oldddudders]

Yeah, of course. What sort of alterations did rationalisation involve though? Were they driven primarily by changes in traffic levels or mainly by changes from steam to diesel haulage? Assuming, for example, a location where traffic levels didn't change significantly, would track changes likely only include the removal of steam engine turning and servicing facilties, or were there other factors?

 

Or is that an unlikely scenario? Did traffic levels change to such an extent during that period that it all went hand in hand?

There were many places where the layout had very long since become a luxury, and thus rationalisation with modern signalling reduced the layout dramatically. Modern signalling also permits much easier use of single lines and reversible working, especially through platforms, as well as removal of maintenance-heavy double junctions and replacement with single leads, without significant loss of capacity. Where a larger signalling scheme, with introduction of a "signalling centre" is an option, opportunities would also be taken to minimise layouts. In the unexpected bouyancy of present passenger traffic, some of those schemes have become an embarrassment, and even needed reversing. Remember that as recently as the late '80s, the civil servants were demanding targetted route-singling, i.e. so many route miles singled per annum, as a virility symbol! It is easy to blame their masters, the elected politicians - but how many of those would have thought of that level of detail?

[Edwin_m]

...as well as removal of maintenance-heavy double junctions and replacement with single leads, without significant loss of capacity...

 

I would say a single lead was a significant loss of capacity, which might not have mattered at the time but may well be a problem today. The most efficient way of using a double junction is to timetable trains to and from the same route to pass on or near it, which you can't do with a single lead.

 

Replacement of double junctions by ladder junctions, using point ends instead of diamond crossings, would have little effect on capacity especially as it may allow higher speeds on the diverging routes so trains can clear the junction in less time.

[The Stationmaster]

There were many places where the layout had very long since become a luxury, and thus rationalisation with modern signalling reduced the layout dramatically. Modern signalling also permits much easier use of single lines and reversible working, especially through platforms, as well as removal of maintenance-heavy double junctions and replacement with single leads, without significant loss of capacity. Where a larger signalling scheme, with introduction of a "signalling centre" is an option, opportunities would also be taken to minimise layouts. In the unexpected bouyancy of present passenger traffic, some of those schemes have become an embarrassment, and even needed reversing. Remember that as recently as the late '80s, the civil servants were demanding targetted route-singling, i.e. so many route miles singled per annum, as a virility symbol! It is easy to blame their masters, the elected politicians - but how many of those would have thought of that level of detail?

 

 

And some of us were busily devising ever increasingly bizarre singling schemes in order to keep Mr Serpell happy - not that he probably understood a single one of them

[The Stationmaster]

I would say a single lead was a significant loss of capacity, which might not have mattered at the time but may well be a problem today. The most efficient way of using a double junction is to timetable trains to and from the same route to pass on or near it, which you can't do with a single lead.

 

 

 

It depends how you measure 'significant' really Edwin, especially as in many cases shorter trains were becoming the norm as well. I don't think we saw any problems resulting on the Western as a consequence of single lead junctions except possibly at Filton - which was one of the first to be subsequent relaid with parallel single leads.

 

In absolute terms I would assess the impact of the average single lead junction as costing two train paths in the opposite direction (over the singled lead) per movement over that single lead assuming a headway of 3 minutes and a junction clearance allowance of two minutes. But in many instances the headway achievable on the singled out route was greater than 3 minutes anyway so the cost was not as great as its theoretical worst impact.

[Stuart]

Looks like decision to change already made but Whitby Town was a four platform terminus with a scissors crossover and no engine release crossovers which lasted well into the DMU era (might have been 1982??)

Have a look at the signal box diagram from The Signal Box

http://www.signalbox.org/diagrams.php?id=173

 

Stuart