The original chicago area transportation study /cats/ method of estimating trips is a hybrid model employing socio-economic variables and land-use considerations. It was thought that a better approach might be to investigate trip generation by purpose of trip. An analysis of cats 1956 home interview survey trips was undertaken to establish factors which had a logical relationship to trip purpose. In addition, data for the factor had to be readily available, there had to be acceptable and reliable forecast methods for the factor, and the factor had to indicate further changes in the destination of the trip purpose under consideration. The estimating methods are best for total, home, and work trips but good for school, social, and personal business trips. methods for estimating shopping trips require further study. Statistically the estimating methods are best at the district level. The statistical results at the zonal level do not invalidate the method in the case of logical, causal factors, but rather indicate the probability of data input error. Total automobiles owned is a direct measure of the total number of trips involved. Together with net residential density, it indicates the propensity of people of make trips. trips to work are directly related to employment, but because of illness, vacation, and other types of absences, the relationship is not completely straightforward, and refined estimating equations were developed. Like work trips, trips to school are directly related to school enrollment with the complication of absenteeism. In the case of social recreation trips, automobile ownership is a good estimator, for it not only reflects trip making propensity but also the tendency of families to exchange visits with other families of like economic and social characteristics. Similar analysis was undertaken for the remaining trip purposes with the result that a complete and statistically valid estimating model was developed for measuring trip generation by purpose of trip. (Author/publisher)
Abstract