Iowa's early experience with the biggest new thing in highway safety appears to be paying off, according to police and highway officials.
"I think theyíve made a tremendous difference," said Coralville Police Lt. Shane Kron. "Itís an impressive system."
Cable barriers -- also called guard cables -- began going up along Interstate highways in Iowa a little over two years ago. They were installed along Interstate 380 in Johnson and Linn counties last summer.
Although the mild winter was undoubtedly a factor, police and rescue personnel say the† cables helped prevent the worst-case scenario: an out-of-control vehicle crossing the median into oncoming traffic.
"Thereís been times the cars hit the median at a pretty good clip, and thereís no question itís stopped them from coming into the oncoming lane," said Lt. Randy Jones, commander of the Iowa State Patrol's Cedar Rapids-based District 11.
"Itís doing its job, itís keeping them from crossing over," said Cedar Rapids Fire Chief Mark English.
Cable strung along a line of posts has been a roadside fixture in much of the country for more than 80 years, according to an Iowa State University report for IDOT (pdf). In the 1990s, several manufacturers developed high-tension cable barriers: three or four cables tightened to 2,000 to 9,000 pounds of tension, supported on breakaway posts and anchored at both ends.
IDOT's five-year plan calls for cable barrier along 210 miles of Interstates 80 and 380 by 2015. The project will cost $13,895,000, or $66,166 per mile. The cables are going up along the stretches with the most median-crossing accidents.
The cables are designed to bring vehicles to a halt in the median. Cable barrier collisions tend to be less violent than those involving conventional solid-steel guard rails, with fewer injuries, according to Cathy Cutler, IDOT's district transportation planner in Cedar Rapids.
"Those posts snap off really easy, and those cables tend to dig into the front end and hold it rather than bouncing it back out," said Jones.
According to the ISU report, cable barriers are relatively inexpensive to install but do require repair costs after being struck.
IDOT hired a contractor last fall to repair damage to cable barriers.† In Cedar Rapids-based District 6, cable barrier has received $146,358 worth of repairs since last Oct. 1, according to Cutler:
- Cables have been re-tensioned twice after minor accidents, at $100 per repair.
- 1,243 posts replaced at $106 each.
- 5 new concrete pads for post footings, at $300 per.
- The assemblies that anchor each end of a cable barrier installation have been replaced three times, at $4,300 apiece.
Cutler said IDOT crews may take over some cable repair when the contract is renewed this fall. For the year ending last June 30, the state spent $767,967 to repair all types of barriers. Cutler noted much cable barrier was installed† after that period, making a direct comparison difficult.
IDOT routinely seeks reimbursement for damaged barriers, signs, and other state property from motorists' insurers.
To keep repair costs down, IDOT has instructed local fire and police departments on removing vehicles from crash scenes without further damage to cable barriers.
"Thereís certain places to cut and not cut" to retain proper tension after an accident, said English.
Research in other states found a high cost-benefit ratio, according to the ISU report. The North Carolina DOT estimates its low-tension cable barriers saved 96 lives and $290 million between 1999 and 2003, but the ISU researchers noted variations in traffic density and other factors make it difficult to reliably estimate cost-benefit factors.
The cables are often going up where there were previously no barriers at all, giving motorcyclists a potential hazard should they leave the road.
"We donít really care for the cable barriers," said Phil McCormick of Clear Lake, state coordinator for the motorcyclists' group ABATE of Iowa. "The steel ones are better. I guess, looking at them, Iíd rather not hit either of them."
Cedar Rapids police records show three accidents in which the barriers were struck. There were no injuries.
In the most serious accident, the cables couldn't halt a dump truck after a front tire blew while the truck was northbound at the I-380 rest areas last Nov. 15. The truck went out of control, plowed through the cable, and dragged it across the median and into the southbound lane, narrowly missing traffic.
Firefighters at the scene said the truck went partly over rather than through the cable barrier.
Darrell Busch of Marion was driving to work at the Veterans Administration Medical Center in Iowa City when his car became entangled in the cable dragged by the careening truck.
"I donít think theyíre safe at all," Busch said of the cables. "Theyíre dangerous."
As Busch's car went under the cables, another truck ran over them, crushing the car's top.
"I had to be helped out of the vehicle because the roof was collapsed on it," said Busch, 55.
Still, the cables prevented accidents from becoming more serious. Kron said cable barriers reduced median-crossing accidents along Coralville's stretch of I-80."I cannot tell you how many times thereís a car that went across the median and almost went into the opposite lane," he said. "Thatís almost a sure fatality."