Bridge Span

Double track width is about 24 feet, so most bridge supports are 28 feet apart
Its not unusual for modern bridges to span four tracks, but even that is 54 feet
I've only seen four bridges that span six tracks, the bridge supports clearly in excess of 76 feet

More common are bridge supports on either side of the outer slow lines (S-F-F-S arrangement)or a single support between the fast and slow lines (S-S-F-F arrangement)

As an example, here are two types in N gauge :
http://m8internet.pwp.blueyonder.co.uk/NGa...ood05-large.htm
The road bridge closest spans all four tracks
The rail bridge further away spans one and three tracks

Thanks M8Internet, much appreciated. Nice layout. I will think I will now go for a shorter span along the lines of the rail bridge in the background.

Hi Peter.

I have been building my layout for 3 years now and with all track laid, scenery and buildings are now being constructed.
I have constructed a roadbridge crossing several tracks.
I constructed it from 1.5mm plasticard and the Wills Varigirder kits.
Once painted and weathered it looks very effective.
Pictures of roadbridge can be seen on my fotopic site http://southcote.fpic.co.uk/