For highly congested areas the increase in the number of lanes is done to accommodate the number of cars on a given route (optimize for capacity). If you can ph

For highly congested areas the increase in the number of lanes is done to accommodate the number of cars on a given route (optimize for capacity). If you can physically fit four times as many cars on a route, but it results in only being able to move at 1/3 normal speed you are still moving more cars over time than a two lane road.