Reproducible features of congested highway traffic

Observation of a four-mile long, inhomogeneous, congested traffic stream revealed that vehicle accumulations between detectors vary with flow in a predictable way, and that a macroscopic kinematic wave with a reproducible speed exists in queues despite unusual traffic behavior. As a result, time-dependent vehicle trip times and accumulations inside long queues (and the queue length itself) can be predicted from readily available data without using any “degrees of freedom” to fit the parameters of a model. Experimental vehicle counts were within 20 vehicles of the predictions for over two hours.