Statistically, Interstates are quite safe for cycling in the majority of the U.S. that allows bicycle access.
The greatest hazard to cyclists on surface streets is intersection conflicts, and Interstate freeways eliminate most of those. There are no left-hooks on the freeway, no failure to stop at stop signs.
Non-interstate highways are much more hazardous.
Last edited by jputnam; 02-10-13 at 12:08 PM.