The concept of the `travel time ratio' is used to investigate the association between work duration and commuting. This ratio is defined as the total travel time (double trip) to reach an activity place divided by the sum of this travel time to and the activity duration at that destination. The concept is based on the assumption that people trade off travel time and activity duration. Data from the 1998 Dutch National Travel Survey (OVG) indicates that people, on average, spend 10.5% of the time available for work and travel on commuting, which corresponds to 28 minutes for an eight-hour workday. Although the variation in travel time ratios is considerable, the authors believe that the maximum acceptable commuting time is dependent on the duration of the workplace visit. Multilevel regression analysis indicates that the travel time ratio is affected by traditional determinants of commuting time, such as personal and household variables. While commuting mode seems to be strongly related to the travel time ratio, urban form factors are relatively unimportant. Finally, it is argued that the use of travel time ratios in land use/transportation policy is a major step forward, since in that case policy would take into account the fact that workers' home-work separation is, among other things, dependent on the time spent at the work location. (A)
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