VOLUME OF TRAFFIC ON THE PRINCIPAL ARTERIES THROUGH THE URBAN AREA In order that data might be available to correlate with the information collected by the Cook County Highway Department, the Survey, through the cooperation of the Department of Public Works, undertook a study of the principal points of congestion throughout the city. More than two hundred intersections along the major routes of travel leading out into all portions of the city have been studied. The relation of some of this data to the material of the county survey is shown in Fig. 2, page 11. CONCENTRATION OF STREET TRAFFIC IN THE CENTRAL BUSINESS DISTRICT By far the most interesting feature of the Chicago street traffic situation is the concentration of traffic in the central business district. For the purpose of the Survey this district has been defined as the area bounded on the north and west by the Chicago river, on the east by Lake Michigan, and on the south by Roosevelt Road. This definition was not made without a thorough knowledge that the area immediately surrounding this district is very important from a commercial standpoint. Certain physical conditions, and a relative density of traffic justify the restriction. This district is slightly less than one mile square. There are few districts in the world which show a comparable density of population and street activity during normal business days.1 The Survey desired to determine definitely the actual number of persons entering this district during a typical day. Through the cooperation of the Chicago Surface Lines, the Chicago Elevated, the steam railways, the electric interurban railways, the Chicago Motor Coach Company, the Department of Public Works, and the staff of the Survey, a cordon count of the district was made for a typical week day in May, 1926. This count reveals a degree of concentration far in excess of the estimates generally made. During the twelve hour period from seven a.m. to seven p.m. of an average week-day it was discovered that 1,693,506 persons enter or leave the central business district. On the reasonable assumption that all who enter leave during the day, this means that during a normal business day the streets of this restricted central district are called upon to carry 846,753 per 1 See frontispiece. sons, or approximately twenty-five per cent of the population of the city proper. The methods of transportation used by this tremendous mass of people is of the greatest significance from the standpoint of street traffic regulation. Table 4 gives this information and Fig. 3 shows the percentages of the total number of persons using various transportation agencies.1 It is significant that the majority of the people who move from their homes to their daily work in the central business district patronize transportation agencies which use the surface of the public streets. Attention is called to Table 5. From Table No. Five it is apparent that the majority of the in 1 For detailed data on the cordon count, see Appendices D and E. TABLE No. 4 SUMMARY OF COUNT OF PASSENGERS ENTERING AND LEAVING THE CENTRAL BUSINESS DISTRICT BY ALL MODES OF TRANSPORTATION, 12-HOUR PERIOD, 7 A. M. TO 7 P. M. TYPICAL WEEK-DAY, MAY, 1926 dividuals who compose the great tidal movements of the population into and out of the central business district daily, must depend upon the ability of the streets to carry the vehicles in which they ride. Every TABLE No. 5 SUMMARY OF COUNT OF PASSENGERS ENTERING AND LEAVING THE CENTRAL morning as the in-town rush begins, the convenience and time of 846,753 workers and shoppers is at stake. Clearly any condition which results in an average delay of even one minute to each of these persons means a substantial economic loss to the community. Obviously, any improvement in traffic conditions which speeds up the movement of this great mass of the population is a definite economic gain. While the above emphasizes the importance of street transportation to city life, the character of traffic concentration in the central business district is best revealed by a consideration of the number of vehicles in which the movement takes place. In order to determine the volume of vehicles a cordon count was conducted by placing checkers at every gateway to the district. These observers were instructed to check all street vehicles including street cars, motor busses, and trucks entering or leaving the district.' A summary of this count is to be found in Table 6. TABLE No. 6 SUMMARY OF CORDON COUNT OF VEHICLES ENTERING AND LEAVING THE CENTRAL BUSINESS DISTRICT, TYPICAL WEEK DAY, MAY, 1926 The figures in the above table reveal the fact that in the central business district there is an entering and leaving movement of 314,640 street vehicles in a typical day from seven in the morning until eleven 1 For assistance in making this cordon count, which is one of the largest single traffic studies ever undertaken, the Survey is indebted to the transportation companies and the Department of Public Works. in the evening. This does not take into consideration the intra-district movements which may be estimated at a figure which would bring the total number of vehicular movements in the district to not far short of a half million per day. Attention is called to the volume of the various classes of street vehicles. Private passenger automobiles exceed all other classes, being 72 per cent of the sixteen hour total. The number of motor cars entering the central district daily is slightly in excess of 30 per cent of the automobile registration of the entire city. Another analysis of the cordon count is presented in Table 7 and Fig. 4. These throw into relation the number of passenger vehicles of various classes, and the percentage of passengers which each carries. It has been discovered in Chicago that the typical passenger automobile operating into and out of the central district, carries an average of 1.8 passengers. TABLE No. 7 SUMMARY OF CORDON COUNT OF PASSENGER VEHICLES AND PASSENGERS ENTERING AND LEAVING THE CENTRAL BUSINESS DISTRICT 12-HOUR PERIOD 7 a. M. to 7 p. M. TYPICAL WEEK DAY MAY, 1926 Another factor in the concentration of traffic in the central district is the use made of the different approaches. In Table 8 the total number of street vehicles is distributed according to their use of the twenty-one streets or bridges at the boundaries of the district. These figures reveal interesting conditions. If the LaSalle Street bridge had been completed at the time of the check the average number of vehicles per artery on the north side would presumably have been 14,080 instead of 16,427. The absence of an Adams Street bridge connection at the present time raised the average per artery on the west side from 10,278 to 11,306. No statistical study could show more clearly than do the figures in this table the difficulties in traffic restrictions created by the bend in the Chicago River. In order that the south side may be put on a parity with the north side with respect to the 1 See also Fig. 2, p. 11. |