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MGS Working Width and Dynamic Deflection

State WI
Description Text

I was reading the consulting summaries and had a few questions.


My first question is on the discussion that Scott, Dr. Faller and I had about the bridge rail retro fit.   During one of our phone conversations it was mention that MwRSF would talk to FHWA about this retro fit option.  Has there been any progress with FHWA?


My second question is on the table of MGS guard rail.  On the standard post spacing, W6x9 mash tests, there is a test where the working width and the dynamic deflection distance is differ only by 0.3 inches. 


If working width is barrier system width plus maximum deflection or maximum vehicle lean and dynamic deflection is measured from back of system, shouldn't the difference between the two measurements be greater than 0.3?  Most of the other deflections and working widths are greater than 0.3" except for the round DF test.


If this result is correct, you may wish to provide a note to discuss why it is correct.

  • Guardrail
Other Keywords none
Date November 1, 2010


The working width and dynamic deflection for test 2214-MG1 was 57.3 in. and 57.0 in., respectively. The working width is the maximum lateral displacement of a post, rail, vehicle, etc. away from the front face of the barrier. The dynamic deflection pertains to the distance between a rail or post location before and during the test. If a rail midspan location has the greatest lateral deflection and the rail becomes partially flattened at this location, then it could be possible for the working width to be only slightly greater than the dynamic deflection However, I would think that this would be approximately 50% of the rail thickness added to the max. D.D. or 58.6 in. versus 57.3 in. We will have someone re-check the high-speed film to determine where the W.W. value of 57.3 in. was obtained.

Date November 1, 2010


The working width point was determined at a midspan between two posts. There was a sign error in the calculation of the working width data. The working width should be 1489 mm or 58.6 inches.

Date November 2, 2010

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