Work zone use of steel plates
MoDOT does not have any specific guidance on the use/placement of steel plates; but they do have the following guidance on signing for them:
From MoDOT Engineering Policy Guide, 616.6.46 STEEL PLATE AHEAD Sign (WO8-24) (MUTCD 6F.46):
“Unprotected excavations or repairs located within a roadway are usually backfilled when workers are not present, but may also be covered with steel plates. While plating is generally used by Maintenance employees on low speed (under 45 mph) roadways, it can also be appropriate within contract and permit work zones.
When plating is used, WO8-24 is deployed as part of Typical Applications 616.8.47a and 616.8.47b. For roadways posted 45 mph or greater, the use of steel plates will require approval from the Highway Safety and Traffic Division and, when project-related, a design exception.
In any case, the plate must be appropriately sized to adequately conduct the vehicular loading and must be delineated according to the diagram below. Only 3/4 in. of the plate’s overall thickness may protrude above the roadway surface and the height differential must be transitioned at a rate no steeper than 3H:1V around the entire perimeter. This may be accomplished by beveling the plate, wedging asphalt or mechanically fastening, as approved by the engineer. Care must be taken to ensure that a mechanical fastener is appropriate for the operating speed of the work zone. The surface of the plate must be treated for skid resistance, either by surface deformation or direct application of a friction course.”