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Iowa DOT is currently working with Illinois DOT in detailing a bridge rail for the new I-74 bridge.  The bridge will accommodate a multi-use trail behind the rail on one side of the bridge.  For this application, we are considering using the Pennsylvania HT rail with a supplemental "sidewalk rail tube" attachment, as detailed in Pennsylvania's standard drawings (attached). 

It is our understanding that the modified post used to support this rail has not been crash tested.  Therefore, we request your assistance in assessing the effect, if any, the modified post and sidewalk rail tube would have on the crashworthiness of this rail configuration, and whether the presence of the sidewalk rail tube in a TL-5 impact could produce flying debris.

Note that we are interested solely in the use of the design shown in the "raised sidewalk section A-A" on sheet 1 of 3 of BD-615M.  Also note that we will not be using the "sidewalk rail rod" or any of its associated hardware.

The TL-5, full-scale crash test of this barrier showed no evidence that the trailer would extend over the steel rail and contact either the back of the posts or the pedestrian rail.  This is due in part to the rail height being 50 inches instead of the standard 42 inches for concrete barriers.  Thus, the box leans on the rail, but the lower corner of the box never extends behind the rail. 

Also, during the crash test, there was very little deformation of the rail.  Therefore, I do not foresee any problems with the pedestrian rail being contacted and turned into flying debris.

The proposed system appears to maintain the crashworthiness of the original (tested) system.