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Guardrail Blockouts

State WI
Description Text

I have some questions about beam guard blocks.


  1. Should a block be allowed to extend below the rail element.  See photo DSC00258.JPG.  My first guess is that this should not be allowed because one of the purposes of the block is to prevent wheels from snagging on the post.  If the block is allowed to extend below the rail, a vehicle may snag on the block.
  2. Is having the block extend above the rail element an issue?   See 2nd Photo.
  • Guardrail
Other Keywords none
Date June 10, 2009
Attachment 2nd Photo.jpg
Attachment DSC00258.jpg


Traditionally, wood and plastic blockouts have extended both above and below the W-beam guardrail element. The blockouts have been either 14 or 14.25 in. long. As such, up to 1 in. of blockout may be exposed above and below the rail. For these situations, upper and lower surfaces are either cut to be horizontal or sloped inward as one moves to the back of the block. For thrie beam systems, we have used shortened blockouts or tapered blockouts to allow the lower corrugation to fold back some to reduce wheel/rim loading or to remain vertical when the rail deflects, thus reducing the potential for vehicle climb up the rail face.


Therefore, we do allow blockouts to extend above and below the rail element. For specific designs, we have modified blockouts to improve barrier performance. For your situations, the blockout size should correspond to those blocks approved for use with the guardrail systems in question.

Date June 11, 2009

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