Did You Know: Longitudinal Traffic Barriers

Did you know that there are three classifications for traffic barriers?

Traffic barriers are roadside safety measures implemented to reduce motorist harm after leaving the roadway. The Federal Highway Administration (FHWA) categorizes roadside medians into three classifications: flexible, semi-rigid, and rigid. These classifications are defined by the deflection of the barrier when impacted by a vehicle at an angle.

Flexible Traffic Barriers

Flexible traffic barriers experience the greatest deflection when struck by a vehicle. This type of barrier primarily halts the momentum of the crashing vehicle rather than redirecting it, reducing the impact felt by the occupants in the vehicle. Typically, flexible traffic barriers require substantial lateral clearance and a gentle slope behind the barrier because of the potentially large deflection. This makes medians on divided highways a desirable location for flexible barriers. High-tension cable barriers are a common selection for a flexible barrier type. In terms of capital cost, conventional flexible barriers are the most cost-effective of the three barrier types. However, due to the high deflection of flexible barriers, they generally require more maintenance or replacement after a collision than semi-rigid or rigid barriers.

Semi-rigid Traffic Barriers

Semi-rigid traffic barriers redirect vehicles back on the roadway more than flexible traffic barriers but less than rigid traffic barriers. Therefore, the impact of the crash can be felt more by the occupants in the vehicle when compared to flexible barriers. In areas with less lateral clearance or less ideal slopes, semi-rigid barriers are generally preferred over flexible barriers since semi-rigid barriers experience less deflection. W-Beam guardrails are a great example of semi-rigid traffic barriers. As noted by the FHWA, semi-rigid barriers are designed to crumble and redirect when moderate to severe contact is made by a vehicle. In the event of a minor crash however, semi-rigid barriers primarily redirect the vehicle, meaning little or no maintenance is required in these minor events.

Rigid Traffic Barriers

Rigid traffic barriers do not deflect when struck by a vehicle. This type of barrier exclusively redirects the vehicle, and the resulting contact with this barrier is almost always the most severe for occupants in the crash vehicle. Rigid traffic barriers are implemented in areas with minimal lateral clearance and/or an unrecoverable slope beyond the barrier. Examples include the use of narrow medians or bridge transitions. New Jersey Concrete Traffic Barriers are a commonly seen rigid barrier type. Conventional rigid barriers have the highest initial cost, yet the lowest maintenance cost of the three classifications of traffic barriers, because typically no deformation occurs when struck by a vehicle.   

The meticulous design of a traffic barrier is just one aspect of overall roadway infrastructure aimed at ensuring safety for all road users. Next time you’re on the road, take a moment to identify and share insights about the different types of traffic barriers with your family and friends! Let’s foster a greater awareness of the measures in place to enhance road safety.