http://atfiles.org/files/pdf/Mountai...west-white.pdf


Key conclusion:

The findings from this study reinforce results from previous research that certain impacts to mountain bike trails, especially width, are compa- rable or less than hiking or multiple-use trails, and significantly less than impacts to equestrian or off-highway vehicle trails.

Note:

Data for the study were collected from 319 sample points gathered from 162.3 miles of mountain bike trails in five common ecological regions of the southwest United States.