UC Davis Institute of Transportation Studies
Structural Equation Modeling of Relative Desired Travel Amounts
- Author(s): Ory, David T
- et al.
The “derived demand” perspective on daily travel, which has become axiomatic in thetransportation field, holds that travel is derived from the demand to participate in spatiallyseparatedactivities. The act of traveling itself is not considered to offer any positive utility, andminimizing travel time is a primary goal of all travelers in all situations. This dissertationcontinues a recent effort to challenge this paradigm by directly modeling the interrelationshipsamong travel amounts, perceptions, affections (or liking), and desires, and, in doing so, asking:why do some individuals want to travel more, and others less? By modeling quantities such astravel affection and desire, I am, importantly, first acknowledging the existence of these measuresand, second, formally quantifying their relative impact on daily travel amounts and each other.Five short-distance (one-way trips less than 100 miles) and five long-distance categories of travelare examined, specifically: short-distance overall, commute, work/school-related, entertainment/social/recreation, and personal vehicle; long-distance overall, work/school-related, entertainment/social/recreation, personal vehicle, and airplane. The models are estimated using data collected in1998 from more than 1,300 commuting workers in the San Francisco Bay Area. Cross-modelanalysis reveals three robust relationships, namely: (1) myriad measures of actual travel amountswork together to affect qualitative perceptions of those amounts (e.g. “a little” or “a lot”); (2)those perceptions are consistently important in shaping desires to reduce or increase one’s travel;and (3) affections for travel have a positive influence on those desires. The second findingsuggests that two individuals who travel the same objective amount may not have the same desireto reduce their travel: how much each individual perceives his or her travel to be is important.The third point argues that the degree to which travel is enjoyed is a key determinant in shapingdesires to reduce travel: the more travel is enjoyed, the less the desire to reduce it. Each of the tenmodels is estimated with the following four estimation techniques: maximum likelihood,asymptotic distribution free, bootstrapping, and the Mplus approach. A cross-model econometriccomparison by estimation technique and sample size is included.The implications of the work are largely theoretical, but the ideas presented can lead to verypractical suggestions. For instance, those promoting travel demand management strategies, suchas telecommuting, should pay attention to the travel perceptions of their target audience. Eventhough someone may be objectively traveling a lot, if the individual does not perceive thoseamounts to be high, he may not embrace a policy aimed at reducing his travel. And the same canbe said for those who enjoy travel: those who see value in travel, perhaps because it provides abuffer between the work and home realms of daily life, will logically be less motivated to reducetheir travel amounts. The survey respondents exhibit a considerable degree of liking for travel ofall kinds studied, and this work unequivocally demonstrates the importance of travel liking totravel behavior.