This issue has been brought up in the past to us as well, and we also have encountered it in testing.
We generally conduct guardrail testing with the bolt on the upstream side of the post for consistency. That said, we have run tests with it on the downstream side as well. We don’t believe that the effect is significant either way.
When you impact a guardrail system, there is lateral loading of the post and longitudinal loading of the post. The lateral loading of the post and compression of the blockout would not really be affected by the post bolt location. With the longitudinal loading, there is some torsion applied to the post through the blockout and post bolt due to tension in the rail. However, the torsion is applied to the post in different directions upstream and downstream of the impact. Thus, changing the post bolt location would not really change the loading of the posts.
Thus, we have generally recommended that states select a consistent bolt location for more uniform installations, but we don’t believe it is required. Guardrail with different connections or terminals may have other considerations, but for the MGS, we would believe this is true.
Thanks
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