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We have a CPSR railing (24" concrete parapet with a steel railing upper.  the bottom width was increased by 1" on the traffic side for aesthetics (max reveal =1/2"). The railing detail was supposed to include a 1" spacer so that the plane of the railing and the plane of the aesthetic treatment would be in the same plane.  The contractor left out the spacer, is there a likely to be a different crash response?

The railing is mounted on a sidewalk.

I seem to recall having numerous inquiries that pertained to variations of the CPSR bridge railing system. A few recent strings occurred in 2019 and 2022. I could not find the original correspondence for which I was more involved several years prior to those dates. Anyway, I am trying to track down the original crash testing history and did not see anything in the 2019 and 2022 emails.

For the detail within the attached PDF, the steel rail is offset forward from the lower barrier face. Does this forward offset correspond to the original crash testing program? There are two considerations on my mind.

Is the steel tube rail detailed to be 1” farther forward than was originally crash tested?

Was there a recommendation or need by VDOT to move the upper steel tube rail more forward to reduce vehicle snag risks on posts through the 12-in. vertical clear opening above the 24-in. tall parapet?

I do not have this background material readily available and am trying to piece it together before commenting on your questions. In the NCHRP 20-07(395) final report, a similar system (S-352 bridge rail) was evaluated using an upper 4x3x1/4 upper rail and a lower rail measuring 2x2x1/8. The upper rail was offset 3 in. away from the post, but a lower rail was positioned to either reduce vehicle snag on the posts or decrease the vertical opening size to accommodate pedestrians. It is unclear as to the exact purpose. The upper rail’s front face was aligned with the front face of the parapet, while the lower rail was setback 1 in. from the front face of the parapet. According to the geometric criteria assessment charts on page 108, a 3-in. setback with a 12-in. vertical opening would result in a reaching the limit of a low snag potential, which is noted as still being acceptable.

For the VDOT system, you are inquiring about having the upper rail (only 1 rail) offset 1in. behind the front face of the rail. If the rail is intended to aid in vehicle redirection, a 1-in. setback could effect barrier performance in some manner, although it is uncertain at the moment as to how much it may be affected.

In 2022, I believe that Bob also recommended trying to maintain the vertical alignment of the upper rail and the front face of the parapet.