The model: Level crossing: markers, the Saint Andrew's cross, and the red flashing light

Every diagonal stripe on a marker post stands for 80 metres: three stripes at 240 m, two stripes at 160 m, one stripe at 80 m before the crossing (Book p.95). Right before the crossing itself stands a Saint Andrew's cross: one cross = one track, two crosses = two or more tracks at that same crossing. As soon as the lights flash red and the bell rings, you stop immediately (Book p.94) — not only once the barriers start lowering.