[Twiglet]

Hi all - I have picked up a couple of ancient ready-made viaducts that fill two gaps in my layout. My concern is that they are a bit big - even the wrong scale (mine is OO). I am looking for something to carry a single track - is 90mm too wide? How wide would a prototype single-track girder-enclosed urban viaduct typically be? 90mm equates to 22'6"

 

[John Webb]

I think this is a fairly narrow double-track viaduct. The typical width for double track over the outer ballast shoulders is around 22ft; track at ground level would also have 'cesses' widening the track bed by another 4 or 5 feet each side.

You could always model the viaduct as a line that has been singled across the viaduct - there are several prototypes where this has happened including Ribblehead on the Settle & Carlisle line. Dewsbury West Midland layout has a single branch line on a viaduct modelled in this way.

Regards,
John Webb

 

[34C]

And further to what John has suggested, during the railway boom years lines were opened as single track, with earthworks and structure in place for double tracking, to enable rapid enlargement if the traffic justified it. But if the traffic didn't grow as hoped, the line remained single track.