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Below is a drawing connecting a sound wall to a concrete barrier.

From my understanding is that our structures department has reviewed this and are satisfied with the structural design. 

Could the L4x4x3/4 bracket that sits on top of the parapet be a snag point?

I have briefly reviewed the 2 pages of details for a new noise wall system. You noted that there exists a 4"x4"x3/4" steel angle on top of the concrete parapet and welded to a vertical W10x22 steel support post. No information was provided regarding the noise panel material, size, or its attachment to the steel posts. You inquired as to the propensity for vehicles to snag on the small angle bracket.

42" Concrete Parapets

For 42" tall concrete parapets, the risk of 2000P and 2270P vehicle snag via engine hood and front quarter panel may be somewhat limited. However, the risk of vehicle snag with 8000S and 10000S single-unit trucks may be increased and depend on the structural strength and integrity of the sound panel material and its attachment to the steel posts.

32" Concrete Parapets

For 32" tall concrete parapets, the risk of 2000P and 2270P vehicle snag via engine hood and front quarter panel on the angle bracket and support posts will likely be increased over that observed for 42" tall barriers and depend on the structural strength and integrity of the sound panel material and its attachment to the steel posts.

It should be noted that we are unable to determine the crashworthiness of this noise barrier system by simply reviewing the provided schematics. The more appropriate means for evaluating the safety performance of roadside hardware is to conduct full-scale crash testing. Let me know if you have any additional questions or comments. Thanks!