A new study shows that the design of 150,000 miles of guardrail in the United States is dangerously out-of-date and unsafe for sport utility vehicles and small trucks.
Researchers from the University of Cincinnati and the Center of Excellence in Dyna Analysis, who used computer modeling to conduct the study, will recommend replacing the guardrail to the Federal Highway Administration (FHWA).
The tests showed that larger vehicles such as pickup trucks and SUVs are more likely to snag on common guardrail systems and roll over, raising the risk of serious injury.
To perform the study, Dr. Ala Tabiei, an assistant professor in Cincinnati's department of aerospace engineering and engineering mechanics, created a virtual reality computer program that simulated vehicles crashing into guardrails.
"The guardrails need to be modified because they were designed 30 years ago. They need to be modified for the new vehicles," Tabiei said.
Replacing all of the guardrails would cost billions, so Tabiei came up with a plan that would be considerably cheaper.
He will recommend changing several parameters of the guardrails – such as amount of spacing between the posts holding the rails, the depth at which the posts are embedded into the ground, and the height of the rails themselves – to allow the system to absorb more impact.
"There will be minimal cost – the only thing they have to do is cut the post and move it," he said.
New guardrail installments can incorporate the new design, he said. Old guardrails must be changed every 10 years according to FHWA standards, so the new design can be implemented on that schedule.
The FHWA, which funded the research and is responsible for guardrail safety, refused to comment on the study.
To get an accurate representation of a real crash, Tabiei validated his model against a previous real-life crash test.
"We found out we needed to change stuff [in our test model], so we did. Ultimately, the simulation captured the experimental test with a very good accuracy," he said.
The study took a year to complete. "If these design iterations would have been done through [real-life] tests only, the FHWA would have spent more than $1 million," Tabiei said. By using computer simulation, the cost was only $50,000.
Nevertheless, other agencies, such as the National Highway Traffic Safety Administration aren't ready to jump on the simulation bandwagon. NHTSA is responsible for determining the safety of vehicles, and test them by crashing cars, trucks, and SUVs into walls or into each other.
"You can't afford to be wrong, so you need a real crash-test result," said Liz Neblett, a spokeswoman for the NHTSA.
Tabiei created the computer simulation model using software called Pr-Dyna. Previous phases of the work were published in the International Journal of Finite Element in Analysis and Design in May 1999, and presented at the International Users Conference in April 1999.
The virtual reality program not only simulates a crash, but also incorporates a virtual crash-test dummy to measure the types of injuries a person would incur. The dummy represents an average-sized male (5 feet 10 inches tall and weighing 170 pounds), and a virtual camera inside the truck records the dummy's movement.
The results showed the dummy's head striking the side window multiple times after the vehicle impacted a guardrail.
Tabiei will submit his report to the FHWA next week.