The Influence of an Expressway on Travel Parameters-the Dan Ryan Study

摘要

To assess the influence of the Dan Ryan Expressway in Chicago on travel parameters, a before and after study was taken. The 'before' survey phase consisted of both roadside interviewing and handing out postcards to the northbound motorists on streets (arterial and local) intersecting the Expressway at midpoint of the survey area. The 'after' survey phase consisted of interviewing and handing out postcards at the same stations, and also handing out postcards on all Dan Ryan northbound ramps and two-thirds of the study area. Additional studies consisted of a complete before and after traffic sampling program on all automobile facilities (local, arterial, and expressway) in the study area, and a speed run in the area. The studies showed that when the expressway was opened, volume decreased on arterials parallel to the expressway and increased on arterials perpendicular to the expressway and which led to expressway ramps. Associated with the change in volume on arterials was a decrease in both the accident rate and the total number of accidents in the area of influence of the expressway. Another part of the report concerned diversion of traffic by facility type and from outside the established limits of the Dan Ryan corridor, and the possibility of determining the amount of traffic that could be diverted from former routes to a newly opened expressway. These analyses, when aggregated, showed that the introduction of an expressway to an area definitely diverted travel from both the lesser grade facilities in the corridor and transportation facilities outside of the predetermined corridor of influence of the expressway. (Author)