You’ve heard of foods, ink, and even fuel made from soybeans. The latest product could keep drivers away from trouble.Iowa State University researchers say they’ve found soy protein makes a biodegradable plastic. The Transportation Department’s testing its use in raised road markers, highly reflective tabs that improve safety in rain or other poor visibility. Road builders couldn’t use them in places like Iowa where they’d hamper plowing in the winter. The new reflectors can simply be scraped off by a snowplow, and in the spring replaced with new biodegradable soy-plastic road markers.