>>1796128>Why does the green arrow come on before the green light at some intersections, but after the green light at others? Difference between lead-lag, lead-lead, and lag-lag; and how protected--permissive control works.
>Why do some lights have the green, but others do not?Green arrow? Visibility, safety, lane configuration, and traffic volume determining gaps in traffic for the left-turn vehicles to cross.
>What is the criteria for an intersection to have a light over a stop sign? Authorities eg FHWA and state DoT will refer to a several-point warrant guideline according to MUTCD and other manuals in the traffic signal warrant study/analysis, perhaps in a larger intersection control evaluation.
>How do they choose how long the lights should be? Math.... But phase and stage length needs to balanced against the whole cycle length too.
>Why do the walk signs come on before the green sometimes? Leading pedestrian interval to allow crossing first for safety and visibility in permissive phase, without changing to a protected phase directly.
>Why does the green stay on after the walk timer has ended?Sorry not in this field, so don't understand your question.
