What really causes traffic jams? Lousy road design, or half-crazed Type A drivers? Why is a roundabout so much safer than an old-fashioned intersection? And do most accidents really happen on well-designed roads during good weather?

Car Talk recently chatted with Tom Vanderbilt, the author of the new best-seller Traffic, about these questions, and weightier issues including his own accidents, the biggest myths about driving — and why on earth anyone would write a book about traffic, anyway.