An approach used by the puget sound council of governments to analyze the regional traffic impacts of alternative major regional transit investments is described and evaluated. because the transit system capacity increases resulting from each alternative were roughly equivalent and the proportion of overall regional travel carried by transit was relatively small, the traffic impacts of the alternatives did not differ significantly on a regional scale. the technical analysis was of a general nature and was aimed at elected officials and the public, who often do not have a comfortable grasp of the meaning and implications of v/c data as they relate to traffic congestion. the problem is more easily understood when presented in terms of length of the peak period or the number of hours of congestion. one of the key elements of the regional traffic analysis was to determinethe length of the peak period on various segments of the highway system. for the purposes of this analysis, length of peak was defined to be the number of hours during which level-of-service e conditionsexist (v/c greater than 0.90). peak-period length was estimated empirically on the basis of the average v/c for a longer time period. alinear regression equation was developed to represent the relationship between 12-hr average v/c and the number of hours of v/c greaterthan 0.90 for a set of actual freeway counts. traffic assignments were plugged into the regression equation to generate estimates of future congestion. the analysis results provided a good sense, not only of relative congestion problems, but also of the magnitude of those problems in absolute terms. the analysis approach proved to be useful educationally as well as simple and straightforward computationally. this paper appeared in transportation research record no. 1142, urban signal systems and transportation system management. for covering abstract see irrd no 817708.
Samenvatting