OKLAHOMA CITY — A state agency spokeswoman says more accidents are being caused by road debris as traffic volume in Oklahoma City increases.

Oklahoma Department of Transportation spokeswoman Terri Angier tells The Oklahoman that traffic volume increased in the city by 35 to 40 percent over the last two decades.

According to the Oklahoma Highway Safety Office, 570 crashes on state highways involved debris as a contributing factor between 2014 and 2016, 166 of which resulted in injuries. Four of the crashes were fatal.

Data by the AAA’s Foundation for Traffic Study show more than 200,000 crashes and 500 deaths nationwide were caused by road debris between 2011 and 2014.

The transportation department says unsecured items are the primary culprit. The agency spends about $5 million annually cleaning up debris from highways.

Information from: The Oklahoman, http://www.newsok.com