INTRAPERSONAL VARIABILITY IN DAILY URBAN TRAVEL BEHAVIOR - SOME ADDITIONAL EVIDENCE

Researchers have used multiday travel data sets recently to examine da y-to-day variability in travel behavior. This work has shown that ther e is considerable day-to-day variation in individuals' urban travel be havior in terms of such indicators of behavior as trip frequency, trip chaining, departure time from home, and route choice. These previous studies have also shown that there are a number of important implicati ons of the observed day-to-day variability in travel behavior. For exa mple, it has been shown that it may be possible to improve model param eter estimation precision, without increasing the cost of data collect ion, by drawing a multiday sample (rather than a single day sample) of traveler behavior, if there is considerable day-to-day variability in the phenomenon being modeled. This paper examines day-to-day variabil ity in urban travel using a three-day travel data set collected recent ly in Seattle, WA. This research replicates and extends previous work dealing with day-to-day variability in trip-making behavior that was c onducted with data collected in Reading, England, in the early 1970s. The present research extends the earlier work by examining day-to-day variations in trip chaining and daily travel time in addition to the v ariation in trip generation rates. Further, the present paper examines day-to-day variations in travel across the members of two-person hous eholds. This paper finds considerable day-to-day variability in the tr ip frequency, trip chaining and daily travel time of the sample person s and concludes that, in terms of trip frequency, the level of day-to- day variability is very comparable to that observed previously with a data set collected almost 20 years earlier in Reading, England. The pa per also finds that day-to-day variability in daily travel time is sim ilar in magnitude to that in daily trip rates. The analysis shows that the level of day-to-day variability is about the same for home-based and non-homebased trips, thus indicating that day-to-day variability i n total trip-making is attributable to variation in both home-based an d non-home-based trips. Day-to-day variability in the travel behaviors of members of two-person households was also found to be substantial.