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I'm looking into providing additional guidance for our staff on the use of temporary crash cushions and sand barrel arrays.

During my reviews, I found NCHRP Report 358 Recommended Practices for Use of Traffic Barriers and Control Treatments for Restricted Work Zone (see attached).  I have the following questions:

1. The sand barrel arrays were designed for NCHRP 230 impacts.  How would the layouts change for a MASH vehicle (e.g. offsets,  barrel layouts...).
2. The guidance on what treatment to use to protect the blunt end of the temporary barrier was based on the barrier being installed for 1 year or less.  If a project will have temporary barrier installed for more than a year what steps should be taken by a designer?
3. Would the charts (figures 4.17-4.24)  have significant changes to the break points between different end treatments because of the new MASH vehicles?  Or do these charts represent the most current state of the art for temporary barrier end treatment protection?

I have responded to your questions in red
below.

1. The sand barrel arrays were designed for NCHRP 230 impacts. How would the layouts change for a MASH vehicle (e.g. offsets, barrel layouts...).

With regards to the sand barrel layouts, MwRSF could look at the barrel arrays and attempt to adjust them. However, we believe that it would be more appropriate for you to contact the sand barrel manufacturers in order to get their recommendations for the barrels arrays with the MASH vehicles.

2. The guidance on what treatment to use to protect the blunt end of the temporary barrier was based on the barrier being installed for 1 year or less. If a project will have temporary barrier installed for more than a year what steps should be taken by a designer?

The end treatment guidance in NCHRP 358 was based on benefit/cost analysis. Thus, the longer the sand barrel array was installed, the more likely that a more robust, long term attenuator would be worth installing. That said, we do not believe that leaving the sand barrels in place for a period over one year hugely problematic. If the barrel array is installed for a much longer time than one year, then you may want to rethink which type of system you use.

3. Would the charts (figures 4.17-4.24) have significant changes to the break points between different end treatments because of the new MASH vehicles? Or do these charts represent the most current state of the art for temporary barrier end treatment protection?

The charts mentioned in NCHRP 358 are currently the best guidance for barrier flare rates n the work zone. No further analysis has been done to update those tables with more recent accident data or to make considerations for MASH.