626.5 Modified Rumble Strips
From Engineering Policy Guide
There may be locations where use of the rumble strip is not possible due to lack of a shoulder with sufficient strength. In this instance a modified rumble strip may be considered. Refer to Standard Plan 626.00.
If used, a modified rumble strip shall consist of a milled rumble strip that is 6 in. wide perpendicular to the pavement. The length and depth shall be the same as for the standard milled rumble strip. The mini rumble strip shall be milled at the edge of the pavement in the normal edgeline location. The edgeline shall then be installed over the milled groove.
Modified rumble strips are not as effective as rumble strips and should only be considered where shoulder width or strength does not allow the use of the rumble strip.