♫ music ♫
Farmer Robert Sentman has lived in his Iowa home more than 50 years.
In that time he’s witnessed nearly as many crashes.
One person died.
The problem is the road curves right in front of his home.
Robert Sentman: “Well, we have had an immense amount of accidents here over the years.
But I kept track, and I have the accident reports up until about three years ago.
I’ve got 48 accident reports.”
Johnson County engineer Greg Parker knew something had to be done.
He worked with the Iowa Department of Transportation to install curve warning signs.
A low-cost safety improvement that made a big difference.
Robert Sentman: “And it has helped immensely.”
More than 25 percent of people who die each year on the nation’s roadways are killed
in vehicle crashes at curves.
Cathy Satterfield: “In some cases drivers don’t slow down enough to make the curve.
In that case they tend to go off the road.
In other cases, drivers just don’t want to slow down, so they’ll tend to cut to
the inside of the curve, and then they can cross the center line and have a head-on collision.”
In fact, 50 percent of the time when someone dies from crashing into a tree in a rural area,
it happens at a curve.
44 percent of all rural fatalities resulting from rollovers and 32 percent of head-on collisions
happen at curves.
Agencies can apply several low-cost safety countermeasures to horizontal curves to help
prevent crashes where similar risk factors exist.
Cathy Satterfield: “We’ve moved more to doing systemic analysis, and what that is
is looking at ‘where are the highest risks?’
So rather than, ‘what’s happened in the past?’
We’re looking ‘where is it likely for crashes to happen in the future?’
And we’re trying to do lower cost improvements over larger sections of the system.”
Pennsylvania experienced a high percentage of fatal curve-related crashes on rural roads
due to the predominance of horizontal curves.
Patrick Wright: “So we studied the local road crash data in Pennsylvania and identified
high priority locations for low-cost safety improvements.
We did the studies and then identified signs, pavement markings, and other low-cost safety
features that help reduce crashes on those curves.”
Basic signing to alert drivers of upcoming curves include things such as advance warning
signs and advisory speed plaques.
Other signs enhance delineation.
Brian Keierleber: “On this particular curve, we were having a series of accidents.
We had two separate fatal accidents, and we knew we needed to do something.
So what we did here is, we put up the chevrons, which is one of the most economical things
you can do and really have some safety impacts.
We also put reflective strips on the chevrons.”
The height, size, retroreflectivity, and location of signs at a curve can increase the chance
the driver is aware of the upcoming curve and will react appropriately.
Cathy Satterfield: “If you need the driver to slow down significantly, then we add an
advance speed plaque to tell them how much they need to slow down.”
A three-year before and after analysis of PennDOT’s effort to enhance delineation
and make other corrections at curves showed that overall crashes dropped 17 percent,
major injury crashes went down 40 percent, and fatal crashes were reduced 44 percent.
For agencies that are paving, FHWA recommends SafetyEdge.
If there are issues with skidding or crashes when the pavement is wet, high-friction surface
treatment can be used.
Creating, maintaining, or improving clear zones in curves also helps.
Cathy Satterfield: “You can’t always keep people on the road.
Some people are going to go off the roadway.
But we can improve the delineation, and we can improve the friction at curves,
and we can make a big difference.”
♫ music ♫