How much space do you need for a Roco Line layout?
Benjamin | TrackDrawer.com · published 2 November 2026
For a closed loop in Roco Line you need an 85 x 85 cm baseboard. A loop with a passing loop needs far more width: the Auto-designer found the first one on 200 x 85 cm, because Roco Line turnouts are slim and therefore long. On 200 x 120 cm double track on R3 and R2 fits with a siding and a small yard, and on 240 x 120 cm double track with two passing loops.
We measured this with the TrackDrawer Auto-designer, using an ordinary stock of Roco Line and a 5 cm clear margin around the board.
The Roco Line radii
Roco Line is H0 track without roadbed, 30 mm wide seen from above. The tightest curve is called R2 and has a 358 mm radius; there is no R1. Then come R3 to R6 in steps of 61.6 mm, the system's track spacing: 419.6, 481.2, 542.8 and 604.4 mm. For broad curves and turnout ladders there are also R9 (826.4 mm), R10 (888 mm) and R20 (1962 mm).
Outside width per radius
The outside width of a circle is twice the radius plus 30 mm. For the baseboard we add 2 x 50 mm of margin.
| Radius | Radius in mm | Circle outside width | Board with 5 cm margin |
|---|---|---|---|
| R2 | 358 mm | 746 mm | 84.6 cm |
| R3 | 419.6 mm | 869.2 mm | 96.9 cm |
| R4 | 481.2 mm | 992.4 mm | 109.2 cm |
| R5 | 542.8 mm | 1115.6 mm | 121.6 cm |
| R6 | 604.4 mm | 1238.8 mm | 133.9 cm |
Each step outwards costs 12.3 cm of depth. Thanks to the narrow track and small track spacing, double track in Roco Line is narrower than in many other H0 systems; a comparison with geoLine is in Roco geoLine or Roco Line.
The smallest loop: 85 x 85 cm
With 84.6 cm as the minimum, that becomes an 85 x 85 cm board in 5 cm steps. The designer lays twelve R2 curves as a circle. On 100 x 90 cm it becomes an R2 oval of 14 pieces and 2.49 m of track, or a skewed loop (a "rhombus") of 16 pieces and 2.60 m.
A passing loop: from 200 x 85 cm
This is where Roco Line differs from most sectional track. The standard turnout 42442/42443 is 230 mm long and diverges by only 15 degrees, with an 873.5 mm radius. To bring the second track parallel, an R10 matching curve (888 mm, 15 degrees) and the 119 mm DG1 diagonal piece follow. Only after 574.91 mm does the second track lie 60.02 mm to the side. On the straight side you make that up with a G1 and a G1/2 (230 + 115 mm).
So a passing loop costs well over 57 cm at each end. Add that to an R2 oval and you get 2 x 575 mm for the turnouts plus 746 mm for the two half circles plus 100 mm of margin: 1996 mm in total. That is exactly where the Auto-designer found the first variant: "Station with two platform roads on R2" on 200 x 85 cm, with 32 pieces and 5.96 m of track. At 95 cm deep, 200 cm remained the smallest width.
If you want a passing loop on a shorter board, more depth does not help; only a turnout with a larger angle would. Roco Line has none in our catalogue; the 10 degree turnout (42488/42491, 345 mm) is even slimmer.
What fits on common sizes?
| Board | What fits (examples) | Pieces | Track |
|---|---|---|---|
| 100 x 90 cm | R2 oval | 14 | 2.49 m |
| 180 x 90 cm | R2 oval, plus siding and yard | 30 | 5.65 m |
| 200 x 85 cm | station with two platform roads on R2 | 32 | 5.96 m |
| 200 x 120 cm | double track R3/R2, plus siding and yard | 48 | 10.42 m |
| 200 x 120 cm | R2 oval with passing loop | 24 | 5.25 m |
| 240 x 120 cm | double track R3/R2, plus 2 passing loops | 54 | 12.27 m |
| 240 x 120 cm | station with two platform roads on R4 | 36 | 7.19 m |
So on 180 x 90 cm, a common first baseboard, a passing loop does not fit yet; the designer fills the loop with a siding and a small yard. What fits on that size per system is in an H0 layout on 180 x 90 cm. On 240 x 120 cm Roco Line reaches 12.27 m, one of the longest results of any H0 system; see an H0 layout on 240 x 120 cm.
Roco Line and flexible track
Roco Line has two 920 mm flexible tracks (42400 with wooden and 42401 with concrete sleepers). On a permanent layout you can use them for curves between R2 and R3, or for a broad sweep where no fixed radius fits. The turnouts and the station stay fixed pieces; you bend the connections in between yourself.
Choosing a board
- Just running trains round: 85 x 85 cm is enough for a circle, 100 x 90 cm for an oval. Extra width mainly gives room for sidings.
- Letting trains pass: allow 200 cm of width, even on a board only 85 cm deep. A long, narrow board along a wall therefore works well.
- Two trains running at once: 120 cm of depth for double track on R3/R2, and 240 cm of width if you also want passing loops.
- Reach: you can comfortably reach up to about 60 to 70 cm from the edge. Stand a 120 cm deep board free or make it accessible from two sides.
Frequently asked questions
Why does a passing loop need so much width?
Because the turnout is slim: 15 degrees and an 873.5 mm diverging radius. It runs smoothly, but the second track only becomes parallel after more than 57 cm. Two turnouts together therefore cost more than a metre.
Is 120 cm deep enough for double track?
Yes. Double track on R3/R2 is 869.2 mm across the outside and fits with margin on 97 cm. On 200 x 120 cm the designer laid it with a siding and a small yard.
Your own baseboard
Look at the Roco Line plans in the Railfolio, or enter your board and stock and let the Auto-designer lay a plan.