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The Ohio standard for permanent concrete single slope barrier has a maximum height differential of 24" between opposing sides (see attachment).  We are trying to track down the origin of this number.  Has there been any research on this topic?  We have a project/design that would like to exceed this maximum.  Would additional reinforcing tied to a footing be necessary and for what additional difference, a couple inches, a foot....?   Thanks! 

We are not aware of any research related specifically to the unreiforced single slope barrier used by Ohio in a grade separated application. 

The design of crashworthy grade-separated concrete median/retaining wall also requires design of the median barrier to resist vehicular impacts and use of lateral dynamic soil pressure in stability analysis. In addition, the design should consider the geometry of the median barrier/wall necessary to meet impact safety requirements, long term durability, capacity of the median barrier/wall sufficient to contain and redirect errant vehicles without overturning and/or causing excessive damage to the barrier, and consideration of variability in soil conditions. Furthermore, the structural design details should enable the barrier to carry vehicular impacts at both interior and end locations. A yield-line analysis is required to analyze and evaluate the steel reinforcement at interior and exterior (barrier gaps) locations of concrete median barriers. The impact load should also be carried near gaps and joints of the median barrier/wall.

The most relevant research we are aware is recent research at TTI with respect to a grade separated single slope barrier for Tennesee. I have attached that research report. It provides a proposed design for a similar installation. However, it is based on a reinforced barrier section. 

Additionally, there is a pooled fund problem statement in development to look at this specific issue in more detail. I can supply you with the proposal if you are interested. 

Take a look at the attached study and let me know if you wish to discuss things further. We would be happy to do so.

Thanks!