Fandangles and Other Measures of Incidental Trips

Abstract

The concept of trip incidentality is examined, with trip incidentality defined in terms of the effect on total daily travel distance of removing (or not recording) specific activities from the daily set of activities. Four measures of trip incidentality are proposed and applied to a travel survey data set collected in Brisbane, Australia, in 2004. Several findings concerning the measurement of daily travel are of importance. Although trip rates have traditionally been used to measure daily travel, it is shown that 50% of trip stages could be removed from the data set, and only 20% of travel time, 8% of trip-stage distance, and 3% of trip chain distance would be lost. These findings question the robustness of using trip rates as the primary means of measuring daily travel patterns, especially when the data are to be used in the development of transport network models. The extent of trip incidentality is further explored as a function of several trip and activity characteristics. It is found that activities are less likely to be incidental if they are for work, education, or recreation purposes and are more likely to be incidental if they are at the end of a public transport trip stage or during peak periods. They appear unaffected by the length of the trip stage preceding the activity but are highly influenced by the duration of the activity itself, with shorter-duration activities being much more likely to be incidental.