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Length of guardrail damage during impact

State IA
Description Text We’re trying to put together some estimates on length of repair for w-beam guardrail and cable after impact. In all of your testing, is there a general longitudinal length of impact for a standard MASH TL-3 test where damage to the barrier exists?

In our hypothetical situation, a vehicle leaves the road and impacts w-beam protecting a culvert. Under ideal and unrealistic conditions, it engages the barrier at the beginning of a standard 12.5 ft section of w-beam and travels longitudinally for some length before being redirected by the barrier. From crash tests and/or your expert opinion, should we estimate that the length of damaged barrier is 25 ft, 37.5 ft, 50 ft, etc.? If both the truck and passenger vehicle damage lengths from a TL-3 test for MGS are available, that would be super, otherwise I’ll take a value for whichever vehicle you’re able to find.

Feel free to call if the above makes no sense.
  • Guardrail
Other Keywords none
Date September 7, 2018


I had a chance to dig up the numbers you requested.


I reviewed our standard post spacing MGS length of need tests under MASH TL-3 impacts with the 2270P vehicle. I looked at the contact lengths and deformed length of the barrier for those tests. Contact length is the general length that the vehicle was in contact with the barrier. I also determined a deformed length which included the length of deformed rail and posts in the testing based on our damage documentation and review of the overhead film.


I reviewed three MGS tests with standard post spacings. Two steel post systems and a wood post system (SYP-1). Results are below.


Test No.

Vehicle Contact Length


Length of Deformed Barrier












As you can see, the contact length may vary somewhat, but the deformed length of the barrier system is pretty consistently around 50’. This would probably serve as a relatively good estimate for damaged system length for a TL-3 impact.


For MGS special applications like long-span guardrail or MGS adjacent to slopes, that distance may increase significantly. Other systems like MGS over curb or with reduced post spacing may have shorter deformed lengths.


Let me know if that answers your question.

Date September 7, 2018

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