This report discusses the scope, magnitude, and root causes of the congestion/saturation problem as determined by a questionnaire survey of traffic engineering professionals and by an extensive set of personal and telephone interviews. In general, the root causes of congestion -- as perceived by these practitioners -- are founded in lack of alternate routes, in land use policies that generate the traffic patterns, and in vehicle-pedestrian conflicts that aggravate the situation. Measures of saturation were identified from a complete review of the relevant literature, a thorough analysis of candidate measures, and a program of field work via time-lapse photography. The results of this work were then used to define a set of appropriate measures and to develop definitions of the various levels of saturation. A range of treatments was studied via simulation -- the UTCS-1 model simulator was used extensively -- analytical methods, and some supportive fieldwork. The various candidate treatments and remedies are discussed in terms of three major categories: 1. Signal: Minimal-response signal policies. 2. Signal: Highly responsive signal policies. 3. Nonsignal: Other treatments in a signalised environment. This report also contains a set of guidelines developed for the treatment of traffic congestion on street networks. The guidelines provide both a tutorial and an illustrated reference in what techniques to consider and how to consider them systematically. (Author/publisher)
Abstract