Essentially you need all streets to be serviceable by trucks, ambulances, etc., and therefore the general minimum is 1 lane. As you add car infrastructure, it becomes relatively more convenient to drive to a destination than take other modes of transport. You are also typically investing in the car infrastructure at the expense of alternatives, a straight opportunity cost and a sort of spiralling trap, as development becomes more and more centred around the car.
Braess’s paradox outlines adding a route can actually worsen overall network flow, and more broadly, new capacity just attracts new drivers until congestion returns to roughly where it started. Suboptimalities like the accordion effect are compounded as more traffic is added to the system.
Induced demand doesn’t imply the current number of lanes is optimal, just that expansion tends to be self-defeating.
Lane reduction alone would just increase misery, so the answer is redirect road space into transit, which absorbs displaced drivers at higher capacity. Otherwise it’s just misery.
I have a civil engineering degree with a focus on transport but never really used it for that, so this is something that I was taught, but had over a decade to devolve more into opinion.
Agreed, mostly. In my neighborhood (Grid system) they updated the 4-lane roads in the area to 2-lane roads with center turn lanes. It’s made traffic much better, simply because there’s no traffic waves created by people lane changing around people turning left.
Essentially you need all streets to be serviceable by trucks, ambulances, etc., and therefore the general minimum is 1 lane. As you add car infrastructure, it becomes relatively more convenient to drive to a destination than take other modes of transport. You are also typically investing in the car infrastructure at the expense of alternatives, a straight opportunity cost and a sort of spiralling trap, as development becomes more and more centred around the car.
Braess’s paradox outlines adding a route can actually worsen overall network flow, and more broadly, new capacity just attracts new drivers until congestion returns to roughly where it started. Suboptimalities like the accordion effect are compounded as more traffic is added to the system.
Induced demand doesn’t imply the current number of lanes is optimal, just that expansion tends to be self-defeating.
Lane reduction alone would just increase misery, so the answer is redirect road space into transit, which absorbs displaced drivers at higher capacity. Otherwise it’s just misery.
I have a civil engineering degree with a focus on transport but never really used it for that, so this is something that I was taught, but had over a decade to devolve more into opinion.
Agreed, mostly. In my neighborhood (Grid system) they updated the 4-lane roads in the area to 2-lane roads with center turn lanes. It’s made traffic much better, simply because there’s no traffic waves created by people lane changing around people turning left.