Concrete safety barrier designs have evolved over the past fifty years as a means to slow, redirect, or stop an errant vehicle from causing a crash with oncoming traffic or traffic in neighboring lanes. They can be used between lanes of opposing traffic (median barrier), at the edges of roadways (roadside barrier), on bridges (bridge rail), as temporary safety barriers during construction, and in many other applications. There are multiple styles and shapes of these concrete barriers and they have changed and evolved with our highway system. Common elements include a 3-inch vertical face starting at the pavement level, then a sloped face, changing back to a nearly vertical face to the top of the barrier, and an overall height of at least 32 inches above the pavement. They have been designed this way so that when a vehicle impacts the barrier, a significant portion of its energy is absorbed in the climbing or lifting action that occurs when the tires roll up the lower sloping face.
Designed and tested by the New Jersey State Highway Department in 1959, the New Jersey barrier was one of the first concrete safety barrier designs to be used on a large scale. During the 1960’s and 1970’s “Jersey Barriers” spread throughout the country and became, the most commonly used type of concrete safety barrier.
During the 1970’s the Federal Highway Administration set out to design a new concrete safety barrier shape that would perform the same functions as the Jersey Barrier, but would have a lower incidence of vehicle rollovers. To this end, the FHA engineered 6 different barrier shapes and labeled them “A” through “F.” After conducting a series of tests, the F-shape barrier was found to have the lowest potential for small cars to rollover upon impact. Thus, the F-shape barrier became one of the approved styles of safety barrier. The only difference between Jersey barriers and F-shape barriers is that the distance from the ground to the slope break point is 13 inches in Jersey barriers, versus 10 inches for F-shape barriers.
Other Barrier Styles
Several alternative styles of safety barrier have evolved over the years. The New Jersey Turnpike Authority, the Federal Highway Administration, and the Canadian Department of Highways have all developed 42” tall alternate versions of the Jersey barrier. These are sometimes referred to as “Federal Barriers,” “Tall Barriers,” or “42 Inch Barriers.”
Movable barriers are a series of interconnected, T-shaped barrier sections, which are hinged together with steel connecting pins to create a movable “chain.” This type of barrier is designed to be picked up and repositioned by a specially designed machine that moves the barriers as it travels down the “chain” of barriers. Portland Bolt also manufactures the connecting pins for this type of barrier.
California and Texas have both developed constant slope style barriers that do not have the standard vertical/sloped/vertical profile of other safety barriers, but rather have one constant angle of slope from pavement surface to the top of the barrier.