Young, Troy M., J. L. Botha, Simon P. Washington, Daniel Sperling (1997) Measurement of Modal Activity Under Varying Traffic Conditions on California Freeways: Preliminary Results. Institute of Transportation Studies, University of California, Davis, Presentation Series UCD-ITS-RP-97-01
This paper describes a research project funded by the California Department of Transportation (Caltrans) that aims to provide a methodology for developing distributions of vehicle operating modes as a function of facility type, and underlying roadway, traffic, and traffic control conditions. These 'modal activity distributions' will provide a link between the macroscopic-level outputs from transportation activity models (e.g., traffic volumes and average speeds) and the microscopic-level inputs required for modal emission models.
The results of a preliminary study conducted on freeways in the northern San Francisco Bay Area are presented here. Loop detectors on the study segment provided macroscopic traffic data, while instrumented vehicles and a helicopter-mounted video camera provided microscopic activity data under a range of traffic conditions. The data collection procedures are described, some technical challenges are discussed, and some results of preliminary analyses are presented. The discussion reveals some limitations of loop detectors and instrumented vehicles, and highlights some advantages of video-based data. The development of a video data analysis system used to decode and analyze the helicopter-based video data is briefly discussed.