TTI Research Supervisor: Akram Abu-Odeh Research Scientist Texas A&M Transportation Institute TAMU 3135 College Station, Texas 77843-3135 (979) 317-2682 [email protected]
Pooled Fund Technical Representative: John Donahue Design Policy and Analysis Manager Washington State Department of Transportation Transportation Building, MS: 47372 Olympia, Washington 98504-7372 (360) 705-7952 [email protected]
The American Association of State Highway and Transportation Officials (AASHTO) Roadside Design Guide recommends that guardrail be installed with the back edges of the guardrail post 2 ft from a slope break. In many mountainous areas, or in locations with tight environmental controls, this width is difficult to provide. As a result, designers often must make a trade-off between reduced shoulder width and a less than optimal guardrail placement (i.e., on the slope past the slope break point). Hence, many state DOTs have a need to place the guardrail directly on sloped terrain. Site restriction might dictate the need for steeper slopes, or placement closer to the slope breakpoint. Another scenario points to the desire to place guardrail on slopes further away from the roadway in order to reduce the number of incidental hits. Hence, developing guidelines for identifying acceptable placement range will be of great benefit to state DOTs.
The guardrail on 6H:1V slope did not meet the performance criteria for MASH TL‑3 longitudinal barriers due to penetration of the guardrail by the 2270P vehicle in MASH Test 3-11.