Extensions to the concept of excess commuting

When people commute to work longer or farther than the actual spatial arrangement of homes and workplaces suggest they could be commuting, people are engaging in excess commuting. In the aggregate, excess commuting is the nonoptimal or surplus work travel occurring in cities because people do not minimize their journeys to work. In this paper an alternative view of excess commuting based on a theoretical maximum commute is presented. The calculation of a theoretical maximum commute allows for an analysis of the range between the theoretical minimum and maximum commutes, which marks an improvement over current approaches to the measure of excess commuting. Conceptually, this range is taken to be the commuting capacity of a city. To what extent commuting capacity is consumed in terms of current levels of commuting forms a primary question of the analysis. A model is formulated and applied to 1990 Census data for a sample of US cities. Numerical and visual results suggest variation in the amount of excess commuting and consumed commuting potential for the sample of cities. The results also suggest a relationship between the jobs - housing balance of a city (as captured by its theoretical minimum commute) and its observed commute. Additionally, the maximization calculation is shown to provide insight into the degree of decentralized urban form. A conclusion is provided which relates the findings of this research to larger issues of urban sustainability.