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|Description Text||MoDOT encounters a wide variety of ballasts across a number of work zone devices and isn’t always sure that they’re acceptable. The Roadside Design Guide (RDG) does not have a great deal to say on the issue of ballast for work zone devices. It speaks only of channelizing devices and says, “The ballast should not present an obstruction if the cone is struck” and then goes on to list double-stacking, heavier devices, sandbags or recycled tire rings as acceptable solutions. The only other mention is that rocks and chunks of concrete are not acceptable.
• Are there any general rules of thumb (material? Height? Weight?, etc.) for ballast that would allow an agency to conduct a visual inspection and deem an installation appropriate?
• Is the RDG guidance enough?
• Do the rules apply to other devices such as moveable barricades and X-base portable sign supports?
• Are the ballasts shown in the attached .pdf acceptable?
|Other Keywords||Ballast, Barricade, Channelizer|
|Date||January 30, 2013|
|Response||We are not aware of any formal guidance on ballasts for channelizing devices, moveable barricades, nor X-stand portable sign supports. Based on the guidance in the AASHTO Standard Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals, the maximum stub height is 4 inches. Therefore, the height to the top of the ballast should not be more than 4 inches above the roadway surface. In addition, the ballast should not be elevated nor should it interfere with the breakaway features of the device. In addition to the RDG guidance, ballasting should be deployed in a similar manner to either the tested configuration or the manufacturer’s recommendation for ballasting
Common ballasts we have seen are sandbags and recycled rings as you have shown in the attached pictures. I would have concerns with placing recycled rings around the center of an X-stand as shown on the second page of the attached photos. This ballast placement could potentially affect the performance of the breakaway mechanism when impacted.
These general rules could be applied to all work zone devices, such as channelizing devices, moveable barricades, and X-stand portable sign supports.
|Date||February 28, 2013|
130 Whittier Research Center
2200 Vine Street
Lincoln, NE 68583-0853
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