An increasing need for quality traffic monitoring data to support transportation program needs is clearly evident as a result of policy changes brought about by highway and clean air legislation. Other contributing factors include the need to monitor transportation program performance, relieve congestion, and enhance intermodal activities. Effective traffic data collection programs are critical to the provision of traffic characteristics data in urbanized areas. The first report, An Overview of Traffic Monitoring Programs in Large Urban Areas , presents results from a survey of urban traffic monitoring activities in the 128 urbanized areas with population greater than 200,000. The survey examined urban traffic monitoring programs, including traffic volume, vehicle classification, truck weight, speed, and vehicle occupancy.
Comprehensive information is provided in generalized table format.
The survey was conducted during December 1995 and January 1996. The objective of the study was to analyze continuous traffic volume, vehicle classification, and truck weight data to identify and quantify variability patterns. Increased understanding of traffic variability will help to improve the statistical accuracy of traffic data, assist in overcoming data deficiencies and limitations, and provide a means to increase the cost-effectiveness of traffic data collection activities. The report summarizes detailed analyses to identify the temporal variation in the traffic data, compare alternative estimation procedures, determine the effect of missing data on annual estimates, examine the effects of holiday and holiday periods, and compute traffic and variability statistics at each site. The information extracted can be used to make determinations regarding the need to adjust traffic estimates to compensate for variability, to track missing data, to aggregate vehicle classification categories to improve the characteristics of the estimates, to assist in the editing of raw data, to monitor changes in traffic characteristics over time, to conduct trend or time-series analysis, and to establish how best to collect the information to improve the quality of the estimates.