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Long Span Guardrail with Curb

Question
State IA
Description Text

Does the long-span MGS function properly when installed flush with a standard 6" curb?  For some reason, I was thinking the area directly below and behind the long-span system had to be free from any snag points or obstacles.


NCHRP 350

W-beam Guardrails

Long-Span Guardrails
Midwest Guardrail Systems (MGS)
Systems to Shield Culverts

Curbs

Date August 27, 2007
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Response
Response
(active)

We had not originally envisioned a 6-in. curb placed in advance of the long-span MGS. As such, we do not have crashworthy details for leaving a post out of a MGS design that is also placed behind a curb. Using our best engineering judgment, it may be possible to consider using the long-span design where 3 CRT posts span each side of the 12-ft 6-in. gap. The one unknown is whether the pickup truck will ride up the unsupported guardrail length after impacting the curb and twist the rail enough to allow vehicle climb and vaulting of the system. However, I do not believe that this undesirable behavior would result. 


Date August 30, 2007
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