Here is my two cents worth of anecdotal data.
I have a long commute, and freeway burnout has put me and my bike on a commuter train.
I really like riding my bike.
The price of gas is not a main motivator for me, but it is a nice benefit.
Reducing my carbon footprint is a bigger motive for me than the price of gas.
I'll comment back on that lengthy report when I have read, or at least skimmed it.
"Mountain bikes (29.7 percent) barely edged out road bikes (28.1 percent) as the most popular commuting bike, followed by hybrids (17.9 percent) and touring models (17.4 percent). Having a second, bad-weather bike was reported by 35 percent of the respondents."
I commute where the is a lot of cycle commuting, and I catch a commuter train with a lot of other cyclists. This survey was done in 1995, but these numbers are supported by my, unscientific, observations, except that I suspect the ratio of hybrids is somewhat higher now.
"Streets with bicycle lanes or marked bicycle routes appear to have less than half the risk of local streets, andbicycle paths, often maligned, were also substantially safer than even
local streets."
This matches my intuitive feeling, and I feel very lucky that my commute includes a lot of this type of infrastructure.