About this simulation
Vehicles arrive at each approach following a Poisson process — random but with a known average rate set by the sliders. The saturation flow rate is fixed at 1800 veh/hr per approach (30 veh/min). Vehicles join the back of the queue and depart when their signal turns green, at the saturation rate. Webster's formula (1958) computes the optimal cycle length that minimises average delay across all approaches. Enable "Auto (Webster)" to let the simulation recalculate every few seconds. Use the N-S green split slider to redistribute green time manually and observe how queues grow on the starved approaches.
Related simulations: Traffic Jams (NaSch) · Queue Theory · Pedestrian Crowd