Mn/DOT's Metro District will test two ways to reduce vehicles crossing the
medians on I-94: a 4,000 feet-long section of four-strand cable barrier and
a 2.3-mile-long area that will be regraded to create a muddy, swamp-like area
filled with cattails.
Mn/DOT received $200,000 from the Federal Highway Administration to fund the
effort.
Although the occurrence of crossover crashes is low, their severity is high—often
resulting in serious injuries or deaths.
The cable barrier will be installed this fall on I-94 near the exit to Weaver
Lake Road in Maple Grove. This section of I-94 experienced six crossover crashes
between 1996 and 2001, resulting in four fatalities.
Nancy Yoo, a Metro design engineer, said the cable barrier has worked effectively
in Oklahoma and other states.
The barrier, she said, will guide vehicles back toward their original lanes.
The average deflection distance is about five feet, compared with 11 feet of
rebound caused by the three-strand cable barriers Mn/DOT uses.
The four-cable barrier is carried on steel posts that slide into a steel sleeve.
A damaged post slides out easily to allow a new one to be installed.
The innovative, swamp-like median will be created on I-94 between Rogers and
where the freeway splits into I-694 and I-494. That area recorded 200 crashes
with injuries from 1996 to 2001. Four of the crashes resulted in deaths.
Loren Hill, traffic safety engineer, Traffic, Security and Operations, said
several factors may contribute to the crossover crashes. They include motorists
traveling at high speeds coming in from the west, relatively low congestion
levels, three or more lanes of traffic in each direction and the change from
a rural to an urban driving environment.
"Whatever the causes, it’s obvious we have to take steps to reduce the
possibility of crossover crashes that frequently result in serious injuries
and fatalities," he said.
Yoo said Metro’s maintenance staff proposed the swampy median as a low-cost,
low-maintenance way to keep vehicles from crossing the median into oncoming
lanes of traffic.
Maintenance crews, she said, will regrade the median and fill it with six to
12 inches of water and plant cattails and other vegetation so it will eventually
become a wetland area.
Dave Engstrom, Metro traffic engineer, said a third area on I-94 which has
experienced a high number of crossover crashes, Brooklyn Boulevard (Hwy152)
to Xerxes Avenue, is being rebuilt and includes permanent, concrete median barriers.
"The cables and the muddy median are experiments," he said. "We’ll
evaluate them to determine their overall effectiveness to reduce crossover crashes."
By Craig Wilkins
|