April 1, 2008 Principles of engineering and physics allow researchers to better understand the steps necessary to improve the design of safety barriers. To optimize the design, mechanical engineers are using computer software to run three dimensional crash tests. They can view the tests from multiple angles, which is vital to understanding how to optimize the design for the types of vehicles on the road today.
About six million car crashes happen every year, with many involving cars and trucks crashing into roadside barriers and signs. Now, Ivanhoe explains how state-of-the-art testing is making roadway obstacles safer.
Most drivers don't even notice roadside barriers, used to prevent cars from careening off the road; but sometimes, barriers become part of the accident. "With these new vehicles, they are more susceptible to overriding these barriers or rolling over when they impact these barriers," Dhafer Marzougui, Ph.D., a mechanical engineer at the National Crash and Analysis Center in Ashburn, Va., told Ivanhoe.
Barriers are tested for safety before they're put on roads; but costly, traditional crash tests offer limited information. Now, mechanical engineers are crashing vehicles the modern way, using 3-D computer simulations -- giving better crash details to help design better barriers. "You can get much, much more information from the computer simulation." Dr. Marzougui says.
Computer software is used to create 3-D models of vehicles and barriers. Then, a crash test is run that can be viewed from multiple angles. Vehicle parts can be removed to get an inside look at damage. Computers show what happens when cars and barriers collide, resulting in new, improved barrier designs.
"The height of the barriers has increased. Now, the new barriers are typically higher than what has been before." Dr. Marzougui explains. Higher barriers improve safety for bigger vehicles and all vehicles in between. "We try to find out the weakness of the barrier and to try to improve that weakness of the barrier through computer simulations." Dr. Marzougui says.
Using virtual reality, researchers are also studying potential falls from ladders, with the goal of improving ladder design.
REDESIGNING CARS ALSO: Cars with crumple zones act more like springs being compressed against the wall, resulting in a cushioning effect, slowing the time it takes for the car to come to a complete stop, and spreading the force over a longer period of time, with less potential for injury. As the car strikes the wall, the front crushes together like an accordion, absorbing the impact and allowing the middle and rear of the car to continue in motion for a short time. By making the time of impact one-tenth of a second longer, engineers can help make the crash have 20 times less force.
RISKS OF SPEEDING: Almost everyone goes a few miles over the speed limit when driving, but recent studies indicate that even a small increase over the legal limit can greatly increase the risks of an accident. Using data from actual road crashes, scientists at the University of Adelaide in Australia found that the risk of a car crash hospitalizing or killing people doubled for every 5 km/h above 60 km/h. So a car traveling at 65 km/h was twice as likely to be involved in a serious or fatal crash, while one traveling at 70 km/h had a risk four times as high. Part of the reason is that a driver has less time to react. On average, drivers react in 1.5 seconds; one who is drunk or distracted by loud music or talking on a cell phone may take as long as 3 seconds to react. And the faster one is traveling, the less time one has to react to a perceived danger.