Friday, December 30, 2011
About cable barrier....
In light of this week's tragic wreck on Eastex Freeway, questions have been asked about whether cable barrier is the best solution for stopping cross-over wrecks.
For those of you not familiar with what happened, 36 year old Johnny Langton of Warren, TX, lost his life after a jeep crossed the median and hit his pickup truck head-on. This occurred, despite the fact there is a cable barrier system along that stretch of highway.
Some say a concrete barrier would have prevented the wreck. Others say cable barrier is the best prevention. What is best? Well, it depends on a lot of factors.
There is one very important fact to remember: No barrier technology exists that will eliminate every wreck. As long as there are vehicles and drivers there will, unfortunately, always be crashes. What transportation officials do is try to reduce the number and impact of those wrecks with the latest technologies available.
Much research goes into testing each device. Engineers do not install protection barrier without it first being test, evaluated and certified to meet specific criteria. Traffic safety engineers spend a lot of time...and money...testing barriers to see how each device operates.
CONCRETE TRAFFIC BARRIER
Despite what some believe, concrete traffic barrier is not always the best solution. Concrete barrier is designed to redirect, slow or stop an errant vehicle, and many times will push the vehicle back into traffic. In other words, it redirects the vehicle back into its travel lane...and into the vehicles around it. Also, concrete barrier is not impenetrable. There have been quite a few instances in our district where vehicles have actually gone over the barrier and into the oncoming lanes. When a vehicle hits concrete barrier there is a good probability it will take out the vehicles around it.
Metal guardrail works very much the same way as concrete traffic barrier except that it is metal supported by wooden or metal posts. However, this type of system is much more high maintenance, as once the metal guardrail is hit, it must be replaced.
WIRE CABLE BARRIER
Cable barrier works very much like the arresting cable that stops airplanes landing on aircraft carriers. Unlike concrete traffic barrier, it cushions the blow, slows the vehicle without throwing it back into traffic, and minimizes the forces on the vehicle and its occupants by absorbing most of the energy of the crash. That is a huge improvement over concrete and metal barrier. Also, research has shown that cable barrier reduces crossover crash fatalities by 90% or more. Many tragic wrecks are avoided by using cable barrier...wrecks that nobody ever hears about because the driver hits the barrier and drives away. We have evidence of this by the amount of repairs made to the cable barrier every week by our maintenance forces. Wire cable barrier has stopped not only cars, but speeding 18-wheelers. And earlier this year, cable barrier stopped a bus from crossing over into the median on I-10 near Winnie.
Is there a perfect barrier system that will stop all wrecks? Unfortunately, no. Not even cable barrier will do that. This latest tragic wreck on Eastex Freeway proves that.
However, what engineers must do is use the latest technologies to try and reduce the impact of wrecks taking place on the highway. So far, cable barrier seems to do the job far better than the other systems available. One veteran transportation engineer went so far as to say cable barrier is "the best safety improvement I have seen in my 30 years with the department."
Hopefully, one day someone will invent the perfect system. Until then, however, transportation departments around the world must use the latest tools available. And drivers must do their part to drive safely and responsibly.