Track spacing: how far apart do two tracks lie?

Benjamin | TrackDrawer.com · published 30 October 2026

Track spacing is the distance between the centre lines of two tracks laid side by side, measured from the middle of one track to the middle of the other. Every track system has a fixed figure for it, because a turnout with its matching curve puts the diverging track exactly that far from the straight one: 77.5 mm on Märklin C track, 61.88 mm on Piko A track, 33.6 mm on Minitrix. Stick to that figure and turnouts, curves and double track fit together without any fiddling.

Why every system has a fixed spacing

Look at what a turnout does. The diverging route curves away from the straight track at a fixed radius through a fixed angle; on Märklin C track turnout 24611, for example, 24.3 degrees on a radius of 437.5 mm. Put a matching curve of the same angle in the opposite direction behind it and the diverging track runs parallel to the straight one again. The sideways offset you end up with is the track spacing of the system.

You can check the figure yourself. A curve of radius R through an angle a shifts the track sideways by R x (1 - cos a). Turnout and matching curve together give 2 x 437.5 x (1 - cos 24.3°) = 77.5 mm on C track. The straight track beside the turnout gets a compensating piece so both tracks end at the same point; on C track that is the 171.7 mm straight next to the 188.3 mm turnout, 360 mm together.

Manufacturers then choose their radii to match. Two circles of radius R1 and R2 are the same distance apart everywhere: R2 minus R1. If that difference equals the track spacing, double track carries on through the curve at the same spacing as on the straight, without extra filler pieces. On C track R1 is 360 mm and R2 437.5 mm: the difference is 77.5 mm, exactly the track spacing. Curved turnouts follow the same logic: the C track curved turnout links R1 with R2, the slim curved turnout R3 with R4.

The spacing per system

The table puts the turnout and the matching curve from our catalogue side by side for each system, with the spacing they give together and the step between the radii.

On most systems the last two columns agree: that is how the manufacturer designed them. On Tillig TT and Fleischmann piccolo the turnout with its matching curve puts the tracks closer together than the step between the radii. If you want double track that continues into a curve on those systems, you need a small extra offset between turnout and curve, or you let the tracks in the curve sit at the radius step and accept the transition. And on Märklin Z the step from R1 to R2 is 50 mm, twice the track spacing: double track at the standard spacing is laid there with R2 and R3.

What goes wrong when tracks are too close

On straight track not much happens: two trains pass neatly as long as their bodies are not wider than the spacing allows. In curves that changes. A long coach rides on two bogies. Between the bogies the middle of the body moves towards the inside of the curve, and the ends beyond the bogies swing outwards. On double track in a curve, then, the ends of the coach on the inner track swing out while the middle of the coach on the outer track moves in. They come towards each other.

A worked example in H0, with assumptions we state openly: a coach 250 mm long with 180 mm between the bogie pivots and a body about 34 mm wide, on C track R1 (inside) and R2 (outside). On R1 the ends of the inner coach swing out by about 10 mm. On R2 the middle of the outer coach moves in by about 9 mm. Together that eats up some 19 mm of clearance. At 77.5 mm track spacing there is a good 43 mm between two bodies on the straight, and still about 24 mm in the curve: plenty. Run the same coaches past each other at 46 mm centre to centre and only 12 mm is left on the straight, and in the curve they touch.

That is why the NEM standards ask for more spacing in curves than on straights, and why it is tempting but risky to lay flexible track closer together than the system intends. The tighter the radius and the longer the stock, the more room you need. A platform between two tracks also needs far more than the standard spacing: allow for the width of the platform plus the clearance beside the train on each side.

How TrackDrawer checks this

TrackDrawer knows the track spacing of every system in its catalogue and uses it for every double track, station and passing loop the Auto-designer lays. In your own plan it checks the distance between tracks lying side by side: if it falls below the minimum (46 mm in H0, 28 mm in N, or the system's own spacing if that is smaller), you get a warning that trains may touch. Rails that overlap are reported as a collision. You see a tight spot on the screen, not only when your first long coach scrapes along it.

Want to know how double track works out with your track? Check the radii you have on the system page, or enter your stock and let the Auto-designer lay double track with a crossover. For a narrow baseboard, read about the dogbone as well.