Although it is not clear exactly when or where the first concrete median barriers were used, concrete median barriers were used in the mid-1940s on
U.S. Route 99 on the descent from the
Tehachapi Mountains in the
Central Valley south of
Bakersfield, California. This first generation of concrete barriers was developed to minimize the number of out-of-control trucks penetrating the barrier and eliminate the need for costly and dangerous median barrier maintenance in high-accident locations with narrow medians.
New Jersey, United States, under the direction of the
New Jersey State Highway Department to divide multiple lanes on a highway. A typical Jersey barrier stands tall and is made of
steel-reinforced poured concrete or plastic. Many are constructed with the embedded steel reinforcement protruding from each end, allowing them to be incorporated into permanent emplacements when linked to one another by sections of fresh concrete poured on-site. Their widespread use in road construction has led to wide application as a generic, portable barrier during construction projects and temporary rerouting of traffic into stopgap carpool and rush-hour reversing highway lanes. Most of the original barriers constructed in New Jersey in the 1950s and early 1960s were not "modular"; they were formed from concrete poured in place. Many of the first installations (Route 46 in Bergen County and Passaic County, for instance) were about tall, much shorter than modern heights. Some dividers on county or local roads may have been lower than that, since they replaced a raised concrete rumble strip that would dissuade, but not prevent, traffic crossing from one lane to another. Route 46 had a rumble strip in many places before the higher barrier was gradually installed. These lower dividers are visible in old photographs. When the
Bergen Mall was first opened in
Paramus, New Jersey, rumble strip dividers were extensively used on the roadway (Forest Avenue) that separated the grocery stores from the mall proper. The design of the Jersey barrier was specifically intended to minimize damage in incidental accidents and reduce the likelihood of a car crossing into oncoming lanes in the event of a
collision. In common shallow-angle hits,
sheet-metal damage is minimized by allowing the vehicle
tires to ride up on the lower sloped face. Head-on vehicle collisions are minimized by gradually lifting the vehicle and pivoting it away from oncoming vehicles and back into traffic heading in its original direction. The
New Jersey Turnpike Authority developed and tested a similar, but heavily reinforced, design. This barrier design has been credited with effectively containing and redirecting larger vehicles, including
semi-trailer (tractor-trailer) trucks. The
Ohio Department of Transportation mandates specific design requirements for their precast concrete barrier walls. The department has marked all compliant precast concrete barrier walls with "350", indicating that they adhere to the requirements laid out in the National Cooperative Highway Research Program's Report 350. Without this marking, a barrier wall is not approved for use in Ohio. ==Variations==