The day-to-day variation of individual trip scheduling and route decisions for the evening commute is addressed on the basis of detailed 2-week diaries of actual commuting trips completed by a sample of automobile commuters in Austin, Texas. The potential impact of using alternative measures of variability in the context of the daily commute is illustrated by comparing a "day-to-day" with a "deviation from normal" approach to individual switching behaviour. Models are presented to relate observed route and departure time switching patterns to the commuters' characteristics, such as workplace conditions, socioeconomic attributes, and traffic system characteristics. About 39 percent of all reported evening commutes contained at least one intermediate stop, highlighting the importance of trip linking in commuting behaviour. These multipurpose trips are shown to significantly influence the route and joint switching behaviour of the commuters. The emerging picture of evening commuting habits clearly suggests high variability of the daily departure time from work, in part due to the trip-scheduling flexibility associated with this trip.
Abstract