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WisDot's Structures Bureau has some concerns over the implementation of the update to NCHRP 350 otherwise known as MASH (see below).  My understanding of the implementation is the following (please correct me if I am wrong):

All existing NCHRP 350 compliant hardware will be accepted to install (this would include existing parapet/barrier designs that WisDot's currently uses), until an AASHTO technical committee decides that there is a performance problem with a specific device or they believe that there are sufficient number of MASH compliant devices available.  A specific time frame after the AASHTO approves the implementation of MASH all new products (eats, crash cushions, parapet designs...) would have to be crash tested using the MASH criteria  (e.g. if 5 years from now WisDOT want to develop a new parapet design they would have to use MASH criteria to crash test the parapet).

**You are correct in stating that existing crashworthy hardware (e.g., 350 approved hardware) will still be allowed to be installed in the future. In addition, I am currently unaware of any date being designated as to when hardware meeting MASH 08 must replace 350 hardware. I personally do not see that happening for a very long time. At the present time, we have been working under the guidance that all new hardware developments occurring after  January 2008, or even early 2008, are to utilize the proposed MASH 08 guidelines. However, if the first test in the program occurred prior to this period, the research and development program is allowed to continue by using the NCHRP 350 requirements.

There are changes to the test vehicles that will increase the amount of force that the barriers will have to withstand; but this change is being driven by changes in the vehicle fleet.  Most experts believe that the majority of TL3 devices will be sufficiently strong enough to withstand the new loads.  It should be noted that in a resent crash testing at MwRSF, TRP-03-190-08, indicated that vertical steel reinforcement had stresses greater that 60Ksi with the existing NCHRP 350 TL3 crash test vehicle.  If the weight limits for semi trucks increased, wouldn't we strengthen our standard bridge designs to accommodate the increase in load?  The same logic would apply to changes in the vehicle fleet for roadside barrier.

**Changes to the mass of the pickup truck used for TL-3 testing will likely increase the impact loads imparted to longitudinal barrier systems. However, this mass change is not deemed significant in terms of impact load nor should it result in any concern for the majority of the existing crashworthy barrier systems. The recently developed vertical parapet was designed to meet TL-3 found in the NCHRP 350 guidelines. In this test, some of the barrier reinforcement yielded and diagonal cracking was observed in the parapet, as was expected from using the yield-line analysis procedures. Although some formwork shifting caused the barrier width to be greater than planned, it would seem reasonable that this barrier system could contain and redirect the 2270P vehicle under TL-3 conditions according to MASH 08. However, increased damage to the barrier would occur. One additional thing to note is that the pickup truck extent over the barrier top would be unknown as well as the resulting vehicle snag on the pier. Barrier translation and rotation occurring due to the additional barrier damage and foundation rotation in the soil would also be unknown for the 2270P test.

**The TL-4 single-unit truck test is expected to result in a much greater increase in the impact loads imparted to barriers. This opinion is based on an increase in vehicle mass from 8,000 to 10,000 kg and a speed increase from 80 to 90 km/h. With these changes, along with a slightly taller vehicle c.g. heights, new stronger barriers will be designed to meet TL-4 of MASH 08 as new R&D barrier projects are funded. However, it should be noted that existing 350-approved bridge railings and barrier systems will continue to be installed into the future and will be allowed to remain in place.

**I do not anticipate any changes occurring for TL-5 barriers.