In 2011, the Ohio Turnpike raised its limit to 70 and recorded its lowest traffic fatality rate ever that year. The higher speed limit attracts travelers to use the safer, limited-access, divided highways of the interstates from more traditional roads. That makes both types of roads safer.
Why does increasing the speed limit on interstates make traditional roads safer?
Explanation
More travelers using safer interstates increases their safety and reduces traffic on traditional roads. This reduction of travelers on traditional roads make those road safer because there are fewer vehicles on them. None of the other answers relate to the information given in the paragraph.