A new pavement treatment used on the S curve of Interstate 380 in Cedar Rapids reduced crashes in its first year, causing Iowa transportation officials to consider using the treatment in other high-risk zones.
The High-Friction Surface Treatment applied in May and June 2012 added a layer of polymer concrete topped with sharp aggregate to increase friction between cars’ tires and the road. That friction helps cars avoid slipping on the curvy stretch.
From June 13, 2012, to June 12, 2013, there were four crashes and one injury on the .3-mile stretch of I-380, compared to an average 10.8 crashes and 5.6 injuries in each of the previous five years, the Iowa Department of Transportation (DOT) reported.
“We think it’s working well,” said Cathy Cutler, Iowa DOT transportation planner.
A 2008 safety audit showed the S curve was the site of many serious crashes. From May 1, 2007, to April 30, 2012, there were 54 crashes causing 28 injuries and $980,000 in damage.
Horizontal curves made up just 5 percent of U.S. highway miles in 2008, but more than 25 percent of fatal crashes occurred on those stretches, the Federal Highway Administration (FHWA) reported.
The Cedar Rapids project cost $494,000 for 1.8 miles of roadway. This included .3 miles over six lanes going north and south.
About 80 percent of that cost was for the materials themselves.
The FHWA paid $50,000 toward the project. The rest was from state safety and DOT funds.
The Iowa DOT also treated three ramps along the interchange of interstates 35, 80 and 235 in the Des Moines area with the high-friction mix. There is not yet post-project crash data from those locations.
State officials are now looking at more potential sites.
“It is not a cheap solution, but it may be beneficial if used in the right situation,” wrote DOT Traffic and Safety Director Steve Gent in an email.
“The goal would be to place the product where we have a pavement that measures low in friction (generally a polished pavement) and an associated high number of crashes related to the low-friction surface. Then we would evaluate the safety of the location along with the durability of the product,” Gent wrote.Research shows the HFST lasts about eight years.