PROPORTION OF DAILY OFFICE POPULATION
ENTERING TYPICAL CENTRAL BUSINESS
DISTRICT OFFICE BUILDING DURING
MORNING RUSH HOUR

ing practically every retail service that can be demanded. They possess their own professional services and amusement facilities. Many of them are equal in size and in the volume of business transacted to the central business districts of medium-sized cities. Practically all of them are sore spots in the traffic system. Too frequently their needs have been neglected, or have been treated in a casual manner. Because of their attractiveness they are the center of a great deal of vehicular and pedestrian traffic.

Their problems are complicated by the fact that the streets must carry not only the local traffic which they generate, but in addition a large load of through traffic due to the fact that they are generally located on principal thoroughfares leading through the city. This concentration of traffic demands has two unfortunate effects. The volume of through traffic complicates business in the neighborhood districts, and the concentration of local traffic tends to tie up the main arteries so that inter-district traffic, and movement through the community is hampered. This condition is aggravated by the fact that merchants are often opposed to traffic improvement which will facilitate through movement, feeling that a congestion in their locality will improve rather than hamper their business. This attitude is based, of course, on a fallacious reasoning which fails to take into consideration the fact that the accessibility of their places of business and the attractiveness of their district as a whole for residential and resultant business purposes, depends upon free and convenient movement of rail and vehicular street traffic. For the solution of the city-wide traffic problem nothing is more necessary than that the conflicts and congestion existing in these business centers on the thoroughfare system of the city should be relieved by suitable uniform regulation.

TIME CONCENTRATION OF TRAFFIC

Thus far this chapter has been devoted to an attempt to analyze existing street use in the city of Chicago by pointing out the reasons for concentration and congestion of traffic at various places in the community. Retarded traffic movements, resulting from excessive demands upon street space, do not come so much from the fact that traffic tends to mass in certain places, as from the fact that it tends to mass at certain times. Population movements over the streets are of a tidal character, generally characterized by a morning inrush and an after

noon outrush. It is significant that with the much vaunted efficiency of the modern city, the most valuable public piece of property, the system of public streets, is used in a most uneconomical manner. One needs only to compare the saturated condition of the central district streets at noon-day, with their practical emptiness at mid-night to realize this. If all the traffic movements in the city of Chicago on a typical day could be spread equally over a twenty-four hour period their would be no congestion at any one place. In fact there would be a high degree of freedom of movement if the traffic demands were spread evenly over a 12 hour period.

The handling of peak or maximum loads has always been a critical problem in the control of street traffic. Community readjustments, looking toward a cutting down of present peak loads on the streets and a filling in of the existing valley, will necessarily come slowly for present practice is based upon old habits. The economic advantages to certain classes of business of transacting their street operations during the night, or even the off-hours of street use, will be so marked that the change will be inevitable.

As business of the city is at present operated there is a comparative uniformity in opening and closing hours, for offices, stores and amusement places. Thus traffic is drawn to and expelled from the districts of concentration, and especially from the central traffic district, in peaks that unnecessarily tax, not only the streets, but, as well, all transportation facilities. Fig. 16 shows the number of people entering and leaving the central business district during a typical week day.

While such readjustments as must eventually be made cannot come readily by law, but rather from voluntary adjustments and agreements, it is proper that something of the character of the existing timeconcentration of traffic should be set forth. Figs. 15a, 15b and 16 show the burden the morning and evening loads place upon traffic and transportation.

A further analysis of the gross movement of persons into the district in the early morning hours is to be found in Fig. 17 which indicates the peak load of persons entering typical office buildings in the central portion of the city. This shows that the peak loads now existing throw heavy burdens not only upon the transportation agencies using the streets, but, as well, upon the sidewalks, and upon the vertical transportation facilities-the elevators of office buildings.