Freeway traffic flow is described in terms of control theory. The detecting elements of millimeter-wave radar sensors, which detect speed and occupancy time by a 61-ghz continuous-wave doppler radar, are used. The regulating unit consists of variable traffic signs fortraffic-dependent speed limit and alternative route guidance. The control unit consists of a local computer and a control center. The control strategy is based on a continuum theory of traffic flow, which takes into account characteristics of the speed distribution for different traffic states. For incident detection and early warning criteria, the model yields the traffic density as a crucial stability parameter. For measuring the traffic density, a correlation technique is presented that for dense traffic uses the radar reflection signals as fingerprints for reidentification of vehicles. This paper appears in transportation research record no. 1320, Freeway operations, highway capacity, and traffic flow 1991.
Abstract