How traffic signals actually coordinate intersection flow, explained

An engineering explainer breaks down how traffic signals manage competing streams of cars, bikes and pedestrians at intersections, describing why at-grade crossings—not lane count or speed limits—set the real capacity ceiling on arterial roads. It frames roadway networks like a circulatory system, with highways as arteries, local streets as capillaries, and arterial roads as the medium-capacity links where interrupted traffic flow becomes the bottleneck.