He’s profiled in the Winter 2011 issue of Deep Foundations, the magazine of the Deep Foundations Institute, in a column titled Dan Brown: Brilliant Engineer, Great Mentor, Down to Earth Guy (p. 35-36 of the PDF).
The section at the end of the article describes his involvement with motorcycles, trials, and the TTC.
Back to the down to earth aspect of Dan Brown, his "lifelong passion" for motorcycles is legendary. He has motorcycled since childhood, and participates at various levels of off-road motorcycle competitions, some possibly death-defying.
Brown is working at continuing this passion with his six grandchildren. The eldest boy was a national champion in the six-year old category two years ago; Brown quickly notes that there weren’t many contenders.
Brown has 600 acres of mountain land where he rides and hosts competitions. The site includes some big concrete pieces of drilled shafts that youngsters like to use as challenging obstacles to ride over, he says.
Motorcycling is a dominant theme indoors, too, says John Wolosick, who reports that a cycle has a prominent place in the Brown living room. Brown verifies that, saying that it is an antique Bultaco Sherpa-T. Professor and co-author Turner, calling him a "wonderful speaker," says that Brown often incorporates humorous analogies to motorcycles in his technical presentations.