Recommendation on Barrier Specification

Every country around the world should require attestation that a longitudinal barrier meets a recognized performance standard before a longitudinal barrier is accepted for use. The two most acknowledged testing criteria for longitudinal barriers are EN 1317-2 (Europe) and NCHRP 350 (United States and Australia.) The TRB AFB20(2) Roadside Safety Subcommittee on International Research is considering a proposal that would recommend that only longitudinal barrier that meets either EN1317-2 or NCHRP 350 be accepted on projects in countries that currently do not have longitudinal barrier performance specifications. This proposal will ensure that properly tested longitudinal barriers are installed and that these barriers will provide the anticipated protection when they are impacted.

Allowing either the US or European criterion to be used will provide economic benefit for the local road authority through increased competition. Since both testing criteria require basically the same light car test (820 kg vehicle – plus dummy weight in NCHRP 350 and 900 kg vehicle including dummy weight in EN 1317-2, 100km/h and 20 degree impact angle) the limiting factors will be the impact severity of the capacity test and the anticipate number of high center of gravity vehicles. A longitudinal barrier that meets EN 1317-2 or NCHRP 350 should be allowed to be used provided the capacity test impact severity of the barrier is higher than the capacity test impact severity of the specified longitudinal barrier. The impact severities of the different levels of barriers in EN 1317-2 and NCHRP 350 are shown in Chart 1 below.

Chart 1 - Comparison of Impact Severity Levels

(click chart to enlarge)

For example, if a road authority decides the most appropriate longitudinal barrier for a road should be the EN 1317-2 “N-2” classification, then any barrier that has an impact severity greater than 81 kilojoules should be allowed as well. This means NCHRP 350 Test Levels 3, 4, 5 or 6 as well as EN 1317-2 Test Levels N-2, L-1, L-2, L-3, L-4a or L-4b also could be used on this project.

If accepted at the upcoming Annual Meeting in January in Washington DC, The TRB AFB20(2) Roadside Safety Subcommittee on International Research would strongly recommend that all road agencies require that longitudinal barriers meet the minimum performance standards as outlined in EN 1317-2 OR in NCHRP 350. A safety factor should be included when determining the severity level to be specified. If a significant number of trucks are anticipated on the road, a higher center of gravity barrier should be specified. Furthermore, the TRB AFB20(2) Roadside Safety Subcommittee on International Research would recommend that impact severity levels be used to specify the minimum capacity for a longitudinal barrier and that any barrier with a higher impact severity level be allowed to be bid on the project regardless if the longitudinal barrier has been tested to EN 1317-2 or NCHRP 350.