Double track spacing:- for UK standards, should be 50 mm (OO/HO) or 25mm (N gauge) centre line to centre line of adjacent tracks. You will find that the track should naturally take up these distances where there is crossover pointwork. Where you have multiple tracks, for example, two fast lines (up and down) and two slow or relief lines (up and down) then the centreline distance between the pairs would be 70mm./

This is not hard and fast especially on the approach to station platforms or bridges. Here a mutual setting of 50mm centre to centre isquite acceptable within the confines of the bridge deck as in Hungerford Bridge across the River Thames from Waterloo to Charing Cross in Westminster, London. Where there is a large station with wide platforms then the distance may be even greater.

Where platform clearances are concerned one of the widest British locos is the GWR Hall class which, in 12 inches to the foot scale (!) is a full nine feet across the cylinders that is 36mm in HO/OO gauge and 18mm in N gauge. On my OO gauge layout I allow from track centreline to platform edge 20mm to ensure clearance. If any of you have travelled to Waterloo on the Northern or Bakerloo lines of the London Tube system you may remember being exhorted to “Mind the gap!” This is because of tight curvature through the station.

During the Second World War locomotives had to be sent wherever required and on several occasions Hall class GWR locos found themselves far from home in the East Midlands and the North of England. Trouble was experienced with contact between cylinders and platform edging. Edging stones were ripped up and scoring occurred on cylinder casing.