The leftmost bar represents a car-only commute; you can see that it gets higher satisfaction ratings (the green part) and lower dissatisfaction (the orange) than both transit and car+transit commutes, which are the next two bars. (Despite the popularity of park-and-rides, there are lots of yucky orange feelings towards a mixed commute.)
But, wait! If you dive into the numbers, it turns out there’s another side to this story. As it turns out, people don’t have an inherent preference for cars, or an innate dislike of buses or trains. The real story is that people don’t particularly like spending time in vehicles, period.
You see, the average bus or train commute takes longer than the average car commute. And once you control for travel time, including transfers, the preference for cars over transit vanishes. Quoting Litman:
The greater dislike of commuting by transit travelers and large city residents can be explained by their longer average commute duration and increased need to transfer. After accounting for these factors the researcher found no statistically significant difference between transit and automobile commuters.
So, taking time out of the equation, people who get to work in a vehicle mostly want to get there as quickly and pleasantly as possible. Other than that, there’s little inherent preference for a car. Corroborating that, Litman cites a recent study of New Jersey commuters in which train users reported that they were happier with their commutes than drivers; apparently, in New Jersey, traffic is bad enough that transit commuting is far more pleasant and predictable than driving.
But according to the research Litman cites (and the chart above), the happiest of all commuters get to work under their own power. Bikers express the highest levels of satisfaction, and least dissatisfaction, with their morning and afternoon treks. Walkers are close behind. I’m not sure if that’s because walkers and bikers tend to have shorter commutes, or because they tend to have pleasant or stress-free routes (otherwise, they’d choose another way to get to work). Either way, it seems like a good way to make people happier with their commute is — if possible — to give them a safe and quick way to get to work under their own power.