Long-Term Vegetation Management Strategies for Roadsides and Roadside Appurtenances (2023) / Chapter Skim
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Pages 101-111
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From page 101... ...
101 APPENDIX E: ROADSIDE SAFETY OVERVIEW A HISTORY OF ROADSIDE SAFETY Highway design was reaching maturity during the 1940s, and focus shifted to safety in the late 1960s. In 1956, President Dwight Eisenhower signed the Federal-Aid Highway Act of 1956.
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102 As transportation facilities continue to expand and most often without the benefit of additional ROW, the most common practice is to shield the obstacle with some type of roadside barrier or attenuator. However, this practice, because of limited ROW, in essence comprises the concept of the clear recovery zone.
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103 Report 153 to address minor changes requiring modified treatment of problem areas. Extensive revision and update to these procedures were made in 1981 with the publication of the 42-page NCHRP Report 230: Recommended Procedures for the Safety Performance Evaluation of Highway Appurtenances.
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104 • Guidance for developers of new safety features • A basis on which user agencies can formulate performance specifications for safety features MASH reflected a changing vehicle fleet in that the small car weight increased to 1100 kg (2420 lb) , the pickup truck weight increased to 2270 kg (5000 lb)
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105 Figure E1. Recommended Test Matrices for Longitudinal Barriers (AASHTO 2016)
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106 • Non-significant modifications of eligible hardware that have a positive or inconsequential effect on safety performance may continue to be evaluated using finite element analysis. Highway safety appurtenances will continue to evolve, and guidance will be updated to reflect changes in the vehicle population and new knowledge about vehicle/safety hardware and vehicle/occupant interactions.
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107 Table E1. Safety Evaluation Guidelines for Structural Adequacy.
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108 Table E2. Safety Evaluation Guidelines for Occupant Risk.
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109 Post-impact vehicular response is a measure of the potential of the vehicle to result in a secondary collision with other vehicles and/or fixed objects, thereby increasing the risk of injury to the occupants of the impacting vehicle and/or other vehicles. Table E3, which reproduces MASH Table 5-1C, provides the guidelines for post-impact vehicular response.
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110 longitudinal axis. In other words, the vehicle cannot be permitted to reach through or over the barrier and reach what the barrier is protecting.
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111 detailed discussion of assessing structural adequacy, occupant risk, and deformation and postimpact vehicular response is given in MASH Sections 5.2.1 through 5.2.3, respectively. A discussion of the supporting research of the same is presented in MASH Appendices A5.2.1 through A5.2.3.
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