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I
have a question for you in regards to B-133.

Current
(2011) AASHTO GDHS 6^thEd., Section 4.4.2 ‘Curb Configurations’

provides
specification of Type B curb (see below) and referenced in B-133.

The
Type B curb height ‘range’ is 4in.- 6in.. Since B-133 specifies ‘Type B

Curb’,
might the install tolerance of 31” MGS combination curb be consistent

w/2011
AASHTO GDHS Type B curb of 4in.- 6in. height? 

The MGS was installed with the face of the rail 6” back from center of the curb face of a 6” tall type B curb. The rail height for that installation was set at 31” from the toe of the curb. We selected the 6” tall type be curb for testing as we believed that this represented a more severe curb for use on high speed roadways. The only more severe curb standard is a 6” vertical curb, but we did not believe that that was applicable for TL-3 situations.

Based on the fact that the MGS was tested with the more sever curb, we have typically recommended that shorter curb heights and less severe wedge type curbs will perform safely when used with the MGS and the same rail face to curb offset.

Let me know if you need further information.