INDOT is currently looking at how we present our sand barrel array standard drawings and maintenance contracts. INDOT currently has 3 sand barrel array devices on our Qualified Materials List for crash cushions. The question that has come up is, can the barrels from different devices be intermix? We have looked though your existing Q&A and it appears the emphasis in mostly put on the weights of the drums and how they are laid out. Our original thought was not to intermix different barrel types but wondered if this really is a concern.
Our question is:
Is there a concern about intermixing barrels from different manufactures of sand barrel array crash cushions, NCHRP or MASH tested?
We don't believe that there would be a huge issue with mixing of sand barrel types. In general, all sand barrel systems function based on the use of the inertial resistance of the snad mass to decelerate vehicles. They also all emply some form of frangible plastic barrel. Thus, they should function very similarly.
That said, they are not identical and mixing of the barrel types would want to consider the following.
1. The barrels should have equivalent mass values to the ones they are substituting. For example, if the sand barrel array uses a 400 lb barrel in the array, one must substitute a 400 lb barrel one of the other types. One cannot substitute in a 300 lb or 600 lb barrel from another manufacturer.
2. The sand barrels typically have some mechanism for elevating the height of the sand in the lighter barrel arrays to better vertically align the mass of the barrel with the vehicle bumper and cg. One would want to ensure that the sand height is maintained similarly between the oriignal and any substitute barrels.
3. Typically, sand barrels are specificed with some recommended spacing to allow them to function properly. Barrels from another manufacturer should maintain similar spacing when used.