Work out green time split instantly with clear inputs, formula shown and shareable results.
Green time is allocated in proportion to each phase's critical flow ratio, so every approach ends up with the same degree of saturation. Total effective green is the cycle length less lost time, and splitting it by the ratio of the flow ratios equalises delay rather than equalising green.
Green split
gi = (cycle - lost time) x yi / sum of all yi
gi = (cycle - lost time) x yi / sum of all yi. Green time is allocated in proportion to each phase's critical flow ratio, so every approach ends up with the same degree of saturation.
Because approaches carry different flows. Equal green over-serves the light approach and starves the heavy one, producing far more total delay than a proportional split.
This calculator takes 4 inputs: Cycle length, Total lost time, Critical flow ratio for phase one, Critical flow ratio for phase two. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.