State records suggest higher interstate speeds have proved fatal for more Iowa motorists. The Des Moines Register reports that rural interstate fatalities are up about 10 percent since the speed limit was raised to 70 mph from 65 mph. Iowa records show 250 people were fatally injured on the rural interstate system between July 1, 2005, and Dec. 31, 2011. The figure was 227 fatalities for the 6 1/2 years before the limit was raised. Traffic deaths on other Iowa highways and roads dropped last year to the lowest level since World War II. Russ Rader with the Insurance Institute for Highway Safety says "the bottom line is that when speed limits go up, deaths go up. When speed limits go down, deaths go down."