Crash data may shape safety policy
 ears ago, when road builders designed grassy medians
as barriers for divided highways, drivers who lost control of their
vehicles and entered the median might dig up a little turf, says Assistant
Professor David Noyce. But over time, highway speeds have increased—and
now more drivers who lose control are careening through the median and
into oncoming traffic, he says. “When you get across that median,
and you’re still going 50 or 60 mph, and somebody comes at you
at 60 or 70, there’s little chance that you’re going to
survive a collision of that magnitude,” he says.
Noyce, who co-directs the Wisconsin
Traffic Operations and Safety Laboratory, is finishing a study of
such crossover crashes that may lead to safer roads and improved divided-highway
safety policy.
As part of the Wisconsin Department of Transportation-funded
study, researchers in Noyce’s group reviewed more than 16,000
police reports for highway accidents that occurred in the state from
2001 to 2003. They found that more than 730 incidents involved vehicles,
tires, disconnected trailers, motorcycles and people who crossed the
grassy median and entered the opposing travel lane. Nearly 20 percent
of these vehicle crossovers became part of a head-on crash on the other
side, resulting in 53 fatalities. “No one expected those kind
of numbers,” says Noyce.
For each of the 730-plus incidents, researchers tracked
crash costs, including everything from vehicle repair or replacement
and medical transport and treatment to injury or fatality costs. With
the data, they are developing some basic crash-prediction models to
help them quantify segments of divided highway in Wisconsin where crossover
crashes are most likely to occur. In addition, they are devising a benefit-cost
modeling procedure that will compare costs of various median treatments
with costs of crashes.
Previously, transportation officials made decisions
about whether to amend a stretch of highway by examining the number
of crashes per mile. But because Noyce’s study filled the “benefit”
gap in the benefit-cost equation, officials now have concrete information
to help them develop criteria for implementing median improvements—or
not—at certain locations.
“Now we can say, ‘It’s this many
crashes per mile, and here’s what the societal cost is of that
many crashes per mile,’” Noyce says. “So what can
we do to counterbalance that in terms of improvements to the roadway
system?”
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