Common rigid barriers used by TxDOT are constant single-slope barriers and F-shape barriers that are cast in place or precast barriers anchored in accordance with TxDOT cast in place barrier standards. Concrete barriers placed in situ or keyed into the roadway pavement are considered rigid barriers. Concrete barriers are placed primarily where little movement of the barrier can be tolerated and typically do not deform when impacted. For concrete barriers that are anchored, between 0 and less than 1-ft of deflection is anticipated for a TL-3 (high-speed) pickup truck impact. Where considerable truck traffic exists (10% or greater) or is anticipated, a TL-4 rated barrier should be considered (minimum height of a TL-4 barrier is 36-inches). Concrete barriers are typically used in narrow medians to limit deflection and reduce the need for maintenance and repair. The exposed ends of the barrier need to be protected by an attenuator.

Semi-rigid barriers commonly used by TxDOT include metal beam guard fence and both pinned and unanchored (a.k.a., freestanding) precast concrete barriers. Semi-rigid barriers have an expected deflection between 24 and 60 inches if impacted by a MASH TL-3 pickup truck under MASH test conditions. Metal beam guard fence is the most commonly used barrier by TxDOT. The current height tolerance for a new installation of a Midwest Guardrail System (MGS) is 31-inches plus or minus 1-inch measured from the road surface to the top of w-beam rail. Metal beam guard fence is used primarily to shield roadside obstacles, such as non-traversable slopes, utility poles, or trees. Precast concrete barriers can be used for temporary or permanent installations. Precast concrete barrier is most commonly used in work zones to shield personnel from traffic and motorists from work zone obstacles.

High-tension cable barriers are the most commonly used flexible barriers. A cable barrier is sometimes referred to as a wire rope safety barrier. It consists of high-tension steel cables mounted on weak posts with a post foundation and anchor terminal. Cable barriers are used as median barriers to reduce median crossover vehicle encroachments.

When transitioning from one type of barrier to another with significant differences in deflection or geometric shape it is necessary to provide a transition between the two barrier types to gradually increase stiffness to reduce the risk of pocketing and/or snagging. TxDOT has several standards for transitions from Semi-rigid (metal beam guard fence) to Rigid barriers available on the webpage. The purpose of all these transitions is to gradually decrease the expected deflection to safely redirect an errant vehicle.

In the application of traffic control plans, situations may arise where transitions are needed from a rigid concrete barrier that has less anticipated deflection to barriers where more deflection is anticipated. The continuum for deflection from less deflection to greater deflection is cast-in-place, precast pinned, and precast non-pinned, respectively. Additionally, a temporary barrier run of 120-ft or less would generally be considered a short run and greater deflection would be anticipated. Refer to the for additional guidance or contact the DES, Project Delivery Section – Roadway Standards and Research Group.