Effects of residential sprawl and household income on travel-time budgets

Using population density as a proxy variable for residential sprawl, this study examines the effect of residential sprawl on the amount of time individual workers spend traveling in a day (for all purposes and all modes), at work and at home. The case study area is the Chicago six-county region. The two principal data sources for this study include the 1990 Chicago Area Transportation Study's Household Travel Survey (CATS HHTS) and Northeastern Illinois Planning Commission (NIPC) data files.; Using path analysis and controlling for various neighborhood/household/individual worker characteristics, the study finds no net effect of density on daily travel time (DTT). This is due to offsetting effects of density on DTT through various travel choices. As density increases, use of public transit increases, resulting in higher DTT. On the other hand, as density increases, both the distances traveled and the trip rates decrease, resulting in lower DTT. Beyond these indirect effects, importantly, the study finds that as density increases, DTT also increases. This positive relationship between density and DTT is explained by the finding that as density decreases, more efficient travel behavior increases through complicated trip scheduling and avoiding periods of congestion. The findings suggest that the amount of time spent on travel by workers living in low-density areas is not different from that experienced by their counterparts living in high-density areas. Workers living in low-density areas increase their DTT by making longer-distance trips and have higher trip rates but they decrease their DTT by arranging more efficient trip scheduling and avoiding peak-hour travel in addition to using faster modes. Therefore, the findings challenge the common view that workers living in low-density areas spend less time with family and at work because of excessive travel.