What counts as a mainline?

[Senex]

Which it was – the South Western Mainline diverged from the London to Exeter/Plymouth 'West of England Mainline'. Which is puzzling because the LSWR was originally the London & Southampton Railway.

I agree with other posters that there isn't a set definition, and it has changed through time.

There are quite a number of examples of where the status of lines has changed over time. Worting is an interesting one, where the London & Southampton was first there and originally the more important, but then the West of England line came to be seen as the principal route (probably principally for its Plymouth traffic), only for the Southampton line to become once again the more important in modern times (and the more important by a very long way!).

As to the general question that started this, I can't offer any sort of real resolution either. I think "main line" has just too many possible usages. And even the sort of proper-name usages are not clear. Is the "East Coast Main Line" just London-Edinburgh, or does it go on to Glasgow/Aberdeen? And dies the ECML include the Leeds branch. As others have asked, just what does the West Coast Main Line" include"? Under "Midland Main Line" do we think just of London-Leicester-Derby-Sheffield, or do we think of the historic Midland Railway main line from London to Carlisle? And so on. And is "main line" the same thing as "principal route"?

 

[Sun Chariot]

"What counts as a mainline"?
I proffer a class 58 in Mainline blue.
And Mainline's class 45 'OO' model.


Oh - main line - I see...

 

[Sunset route]

So the Brighton main line starting from London Victoria is listed on signalling diagrams as
the Down & Up Brighton Fast and Slow lines,
the Down & Up Victoria Fast and Slow lines,
the Down & Up Fast and Slow lines,
the Down and Up Quarry lines,
the Down & Up Redhill lines,
the Down & Up Fast and Slow lines
and finally from Balcombe Tunnel Junction to Montpelier Junction as the Down and up Main lines.

Also the track engines (pway etc etc) use the reference code VTB (Victoria to Brighton) but collectively we all call this route the “Brighton Main Line”.

So a main line can be used to give a section of track a name or it can be also a term applied as a marketing tool for a line of route between two or more places and I’ve also never come across any hard rules for a true definition.

 

[zwk500]

So a main line can be used to give a section of track a name or it can be also a term applied as a marketing tool for a line of route between two or more places and I’ve also never come across any hard rules for a true definition.

Indeed - especially in GWR land where the track pairs are often 'Main' and 'Relief' rather than 'Fast' and 'Slow'.

 

[Annetts key]

Indeed - especially in GWR land where the track pairs are often 'Main' and 'Relief' rather than 'Fast' and 'Slow'.

Always in GWR land
Why admit that you have "slow" lines

 

[Sunset route]

Indeed - especially in GWR land where the track pairs are often 'Main' and 'Relief' rather than 'Fast' and 'Slow'.

Always in GWR land
Why admit that you have "slow" lines

In our part of the old SR land we used to have Through and Local in multiple track areas until the BML resignalling of the early 80s came along.