Traffic flow analysis

Traffic flow analysis measures how vehicles, and increasingly cyclists and pedestrians, move through a road network: volume at a point, speed over a segment, and density, the number of vehicles per lane-mile. Together these describe whether a corridor is flowing freely or approaching the breakdown point where small disruptions cascade into major congestion.

Data comes from loop detectors, cameras, probe vehicles, and smart city sensor data more broadly, and is often paired with Origin-destination (O-D) data to explain not just how much traffic exists but where it is going. This differs from simple traffic counts: flow analysis looks at the relationship between volume, speed, and density together, since a road can carry the same vehicle count at very different speeds depending on how congested it already is.

Cities use flow analysis to time signals, justify capacity projects, and run route optimization for emergency and transit vehicles, and it is a direct input into evacuation modeling and long-range land-use modeling. A common pitfall is treating a single unusual day, a holiday, an accident, a special event, as representative of typical conditions, which leads to infrastructure decisions sized for the wrong scenario.