Selection, Installation and Maintenance of W-Beam Guardrail End TerminalsThis brief provides general guidelines regarding the selection, installation, and maintenance of W-beamguardrail terminals. In addition, common issues of concern are identified for these elements withgenerally accepted practices to address these issues.
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The American Association of State Highway andTransportation Officials (AASHTO) Roadside Design Guide 4th Edition Chapter 8.3 provides additionalguidance on terminal design concepts. Terminal Selection:There a re three primary W-beam guardrail end terminal designs in use at present: Burke-in-backslope,non-energy-absorbing, and energy-absorbing.
Figure 1 shows th e relative trajectories of avehicle impacting non-energy-absorbing and energy-absorbing terminals head-on and at high speed(62 mph). The decision to use either an energy-absorbing terminal or a non-energy-absorbingterminal should be based on the likelihood of a near end-on impact and th e nature of the recoveryarea immediately behind and beyond the terminal.Figure 1: Vehicle Trajectories by Terminal Type Characteristics of the Different Terminal Types:.Non Energy-absorbing – A terminal that does not dissipate a significant amount of kinetic energy in a head-oncrash and is a gating system that allows the vehicle to traverse the area behind and parallel to the guardrail. Some key characteristics include:. Does not significantly reduce vehicle speed in a near head-on hit. Run out distance can exceed 150 feet.
Best specified when t here is a long, clear, traversable area behind and parallel to the guard rail installation,such as often found in a flat freeway median.Energy-absorbing - A terminal that dissipates a significant amount of kinetic energy in a head on crash. Some key characteristics include:. Barrier installations less than 150 feet in advance of any shielded object must be energy absorbing. Energy-absorbing – terminals have been shown to stop an impacting pick-up truck in about 50 feet when struck head-on.
Best suited to locations where traversable area behind barrier is limited; or, contains fixed object hazards.Buried-in-Backslope – A terminal that terminates a W-beam guardrail installation by burying the end in thebackslope. Grading is critical for a buried-in-backslope terminal because the terrain leading up to the buried-in-backslope must be traversable and contain no fixed object hazards. If the backs lope is relatively flat, avehicle can ride up the slope and bypass the terminal. When th is condition exists at a site, the designer mustensure that the hazard remains shielded by assessing the available clear run out distance behind the rail andthe barrier length-of-need.
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The 'grading platform' in thephoto has a drop-off thatcreates a significantly greaterhazard than previously existed.Advance Area:The 'advance area' consists of thespace traversed by an errantmotorist before the terminal isstruck.
Sea lamprey barrier with trap and sort fish ladder on Trail Creek in Michigan City, Indiana. Photo Credit: USFWSThe barrier team from the Sea Lamprey Control Program’s Marquette Biological Station annually operates and maintains sea lamprey barriers throughout the Great Lakes. There are 46 barriers specifically built to block sea lampreys and 27 other structures that were modified to function as sea lamprey barriers to prevent migration upstream and infest suitable habitat.In addition to the sea lamprey barriers, the team completed inspection of 371 dams during 2015 that were previously identified to impact the Sea Lamprey Control program if the structure should fail or be removed. Inspection information is used to ensure the barrier continues to block sea lamprey migration and identify repair or rebuild projects.Dam removals have increased during the last several years and pose a significant threat to the success of the program. The barrier team completed 45 consultations with partner agencies on proposed dam removals or modifications. Sea Lamprey Control Program recognizes the importance of striking a balance between improving connectivity of watershed for the benefit of native species and limiting access of invasive species, such as the sea lamprey, to areas upstream of existing barriers.Planning for barrier construction on the Grand, Little Manistee and Manistique rivers in Michigan, the Grand River in Ohio, the Cattaraugus River in New York and the Bad River in Wisconsin continued during 2015. Construction on the Grand River sea lamprey barrier is targeted for construction during 2017, while others would likely be constructed during 2018 or beyond.The Sea Lamprey Control Program continues to work closely with others to control populations of sea lampreys in tributaries of the Great Lakes, to protect the fishery and related economic activities in the basin, an estimated annual benefit of $7 billion per year to the region.
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Fish and Wildlife Service deliver a program of integrated sea lamprey control in the U.S. Waters of the Great Lakes in partnership with the Great Lakes Fishery Commission. For more information, contact Greg Klingler at 906-226-1209.Contact Info: Gregory Klngler, 906-226-1209,Find a Field Notes Entry.