Signal Spacing Calculator — Realistic Placement

In real life UK colour-light signals are spaced a full braking distance apart — roughly 1065m at 60mph, up to about 1330m at 70mph. Scaled literally that is 14-20 metres in OO gauge, far too long for any home layout. This is why the calculator shows a recommended COMPRESSED spacing alongside the true scale distance: most modellers use about 600-1000mm in OO gauge, which reads convincingly without needing a football pitch. The default 95% compression lands inside that band.

Choose based on your era. Semaphore signals suit steam-era layouts (pre-1960s). Colour lights suit modern-image layouts. Transition-era layouts (1960s) often mix the two — colour-light distants under semaphore stop arms were common. Check prototype photographs for your chosen location and period.

UK semaphore signals stand about 8m tall (105mm in OO at 1:76.2). Colour-light signals are about 5.5m (72mm in OO). Ground signals are about 1m (13mm in OO). Commercial signal kits from Dapol, Ratio and Berko are made to correct scale heights — a Dapol motorised OO semaphore measures around 105-108mm, matching the 8m prototype.

Place home signals on the approach side of points, and starter signals at the departure end of platforms. On semaphore lines a distant signal sits roughly a braking distance (about 400m real) in rear of its home signal. On a model, compress these distances proportionally using the compression control so the relationship still reads correctly in the space you have.