The California Department of Transportation (Caltrans) and the U.S. Federal Highway Administration (FHWA) conducted a Field Operational Test (FOT) to evaluate the benefits a mobile surveillance and wireless communication system provides in support of freeway surveillance, ramp metering, and arterial traffic management. Six surveillance and three ramp meter trailers were designed and built. A retransmission or relay site and data reception equipment for use at traffic management centers and research facilities were also installed. The FOT showed that the compressed video imagery transmitted from the trailers facilitated control of arterial traffic signals at preplanned special events. The local responsive freeway ramp metering algorithm in use by Caltrans reverted to the prestored time-of-day rate during rush-hour traffic flows when either the inductive loop detector (ILD) or video image processor (VIP) data were input to the algorithm. Thus, the algorithm was not sensitive to the differences in mainline flow rate and occupancy measured by the ILDs and VIP during the heavy traffic encountered in the test. Data were shared effectively among state and city traffic management centers and university research facilities over spread spectrum radio links. (A*)
Samenvatting