Good Practice Localized Bottleneck Reduction - System Wide Adaptive Ramp Metering (SWARM) Project (California)

In short, the SWARM system uses detectors to feed algorithms that forecast when and where congestion will occur. The system then "adapts" to control upstream ramps, through metering, to control congestion on the mainline.

SWARM forecasts the traffic state at predetermined problem points (bottlenecks), and adjusts metering rates based on forecasts. It treats the freeway network as sections. Each section is defined as being between two successive detectors that have reliable data outputs. The operation of SWARM is based on traffic density, with the goal of maintaining real-time density below a pre-determined saturation density for each section of freeway.

Currently CALTRANS District 7 operates the SWARM technology and serves as an incubator agency to help distribute the system to other California highways.