Nonwork Travel times and City Size: Testing Variances as Well as Means

Relatively little attention has been paid to the relationship between travel time variances and city size. We utilize 2009 Nationwide Highway Travel Survey data and test the relationship between metropolitan area nonwork (home-based shopping and social/recreational) trip time means as well as variances with metropolitan area size. We include tests for metropolitan areas as a whole and for residents from included Urban, Suburban, Second City, and Town and County subareas. OLS regression analysis shows some estimated slopes are not statistically significant, and none is much greater than zero. Nonwork travel time means and variances are highly correlated. These relationships are also invariant with respect to the sub-area place of residence. Whereas urban economists have emphasized the co-location of linked firms as part of their interest in agglomeration economies (see, for example Quigley, 1998, in particular his Table 1), we cite and build on literature that provides evidence for the co-location of workers and jobs hypothesis. Average trip times do not rise appreciably as metropolitan population increases, regardless of trip type. We conclude that our results here are additional, although indirect, evidence that the co-location hypothesis extends to nonwork travel and location behaviors.