The Communal Nature of Travel
Nile River, Feluccas on the Nile River and Old Cataract Hotel, Aswan, Egypt Wall Mural
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Up to now, no attempt has been made to define the behavioral unit. Logic suggests that the pertinent unit of analysis is the household--a collection of individuals who choose to reside together. For certain economic activities, each individual acts independently irrespective of household ties. For others, the household acts as a unit; for example, in the purchase of housing facilities.
In the case of urban travel, arguments could be advanced on both sides. Some trips are clearly initiated by individual household members without regard to the rest of the household. For other trips, such as shopping for groceries or earning a livelihood, the travel decisions probably represent some collective decision. Social-recreation and business trips are probably the outcomes of joint decisions. Thus, although the household appears to be the pertinent unit of analysis, cognizance must be taken of the size and composition of its members.
Consider the impact of household size and composition on the demand for trips. In all likelihood, a minimum number of trips will be demanded by each household, as a unit, simply for its maintenance. These would probably be productionoriented trips for work or for the maintenance of the household. In larger households, more than one member may belong to the labor force; the likelihood of this event would depend on the age and sex composition, as well as the income of the household head. The impact of household size on travel demands would probably be more pronounced for consumption-oriented travel. The demand for leisure activities would depend on the number of persons in the household with appropriate adjustments for income and the age composition of the family. Where young children are present, the likelihood is quite remote that they will participate in weekday travel for purposes other than attending school or accompanying mother to shopping.
Suppose that the age-sex composition of households is neglected. What then will be the probable impact of household size on travel demands? One would expect household size to be positively related to the number of trips demanded for two reasons. First, production-oriented trips will increase with size, because of the greater likelihood that more than one member will belong to the labor force. Second, larger households would demand more consumption-oriented trips, since these should be more directly related to the number of adult members. Finally, since larger households typically contain larger proportions of young children, the demand for trips should increase less than proportionally to the number of persons.