High-Performance barriers are often utilized in areas where tractor-trailers and similarly larger vehicles are frequently present. Since these trucks have a higher deck than the average vehicle it is important to not only provide the added height, but to also give stronger support at the top of these barriers. Without the added support, these larger vehicles would impact the top of the barrier and simply roll over them into oncoming traffic or off raised roadways. The impact would also cause spalling, projecting portions of the barrier into oncoming traffic. Thus, the use of reinforced concrete glare screens has been adopted in many applications as an additional preventative to this occurrence.
Along many New Jersey highways a 42 inch concrete median barrier has been installed to assist in containing tractor trailers and other larger vehicles while redirecting them back to the roadway. These median barriers are often set into the roadway giving them added support and preventing them from turn over on impact. The uppermost portion of these barriers is also heavily reinforced to absorb the impact from these larger vehicles.
The New Jersey Turnpike Authority (NJTA) has crash-tested and developed a 1070-mm- (42-in-) high concrete median barrier that can safely contain and redirect tractor-trailers to an upright position. This barrier is made with the NJ-shape forms. The 75-mm vertical reveal is covered up with asphalt to anchor the barrier against overturning. (See figure 2.) This turns the barrier profile into an F-shape that does not have a vertical reveal. The NJTA’s Heavy-Vehicle Median Barrier is 305-mm- (12-in-) thick at the top. It is heavily reinforced.
Despite these added safety precautions some states do not utilize the thicker barrier tops even though there is a chance that spalling can occur on impact. History has shown that these incidents are extremely rare and do not warrant the added costs of the thicker barriers.