SPECIAL-PURPOSE TRAVEL SURVEYS

Regional travel forecasting models often assume that trip-generation rates are stable over time. Though the validity of this assumption is confirmed with regard to overall trip rates per household, the assumption is less applicable to disaggregated trips. It is the contention of this paper that because of the demographic and labor-force transformations of the 1970s and 1980s, the composition of person trips has changed through a relative decline in the share of home-based/nonwork trips, as well as through an absolute drop in the average number of these trips per household. Paralleling this decline has been a rise in the shares and numbers of home-based work and non-home based trips. A comparison of the results with other metropolitan areas suggests that, in general, rates for special-purpose trips are more likely to be stable cross-sectionally than intertemporally. According to the 1984 Dallas-Fort Worth travel survey, an average household made 8.68 trips per day, a rate that has remained fairly stable since 1964. Person trips per person and vehicle trips per person, however, have had a pronounced increase since 1964 reflecting the smaller household size and lower automobile occupancy rates of the recent decade. The results of the 1984 travel survey also indicate that (a) the average trip length in the metropolitan area is about 7 mi, (b) the average trip duration is 17 to 19 min, (c) the automobile occupancy rate is 1.13 for work trips and 1.5 for nonwork trips, (d) the transit mode share is 1.7 percent, and (e) the peak-hour travel time is between 7-8 a.m. and 5-6 p.m.