A very interesting study on commuting and public health was recently released in Sweden. While the generalizability of findings from a study of a relatively homogeneous population is always a bit suspect, the fact this analysis includes the results from 21,000 commuters in a densely populated part of southern Sweden with a wide range of commuting modes available make it worth perusing. (Notably, 71 percent of the commuters travel by primarily by automobile, and the number of cross-border commuters (to Denmark) has risen dramatically in recent years.)
In "Relationship Between Commuting and Health Outcomes in a Cross-Sectional Population Survey in Southern Sweden," Erik Hansson and his coauthors found that the relationship between commuting and personal health effects is complex but significant. In general, the longer the commute, the lower the reported health outcomes as measured by sleep quality, stress levels, mental health, absentee days due to sickness and other indicators. No surprise there, at least intuitively.
But, here's the interesting part: Health indicators consistently deteriorated for public transport commuters as commuting time when up, but not for car commuters. The relationship was concave downward for car commuters where health indicators deteriorated until around 60 minutes (for a daily commute), and then improved for the longest commutes (see the discussion on pages 14-17 of the full study). Car commuters in the longer time cohort tended to have better paying jobs, more control over their work environment (managers), live in rural ("green") areas, and work more overtime. While the specific reasons for the lower levels of stress and health were not clearly identifiable, the researchers speculate that those with longer commutes probably spend a fair amount of time in relatively uncongested rural parts of the county. They are probably also happy with their trade-off of higher pay with the ability to live in a rural setting. Public transit riders may experience lower public outcomes because trains and buses often can be stressful as commuters wrestle with potential delays, making connections, transfers, and keeping track of stops. "Active commuters" (walkers and bicyclists) had the best health outcomes, and all reported daily commutes of less than 30 minutes.
The results are intriguing. In particular, similar work in the U.S. would be useful if it can highlight the kinds of trade-offs implicit in housing and commute choices. If people are voluntarily choosing longer commutes for perceived benefits from superior living environments, then maybe we should be spending less time focusing on the length of commuting in terms of distance and more time on reducing congestion.