Guide to Steel Road Plate Usage
Steel road plates provide temporary coverage across trenches, excavations, utility cuts, and other openings where access must be maintained during construction.
Proper road plate selection depends on plate thickness, clear span, supporting conditions, traffic conditions, overlap, anchorage, and the applicable tabulated data.
Steel Road Plate
Temporary excavation and roadway coverage
What Are Steel Road Plates Used For?
Road plates, also called trench plates or crossing plates, are used to temporarily cover excavations and maintain access while construction, utility, or road work is underway.
They are commonly used where vehicles, equipment, or pedestrians need to pass over a trench or excavation while the work below remains incomplete.
The plate must be selected and installed for the actual opening, support conditions, traffic conditions, and project requirements. Plate dimensions alone do not determine the allowable clear span.
The plate must be supported and used within the applicable tabulated data. Any span beyond the published limits requires additional engineering.
Steel Road Plate Specifications
The specifications below are based on minimum ASTM A36 steel with a yield strength of 36 ksi and the HS-20-44 traffic loading criteria referenced in Iron Lot's road plate tabulated data.
The maximum allowable span is the unsupported distance the plate is permitted to bridge under the referenced design conditions. It should not be confused with the overall width or length of the steel plate.
| Plate Thickness | Maximum Allowed Span | Common Sizes (ft) | Weight Range |
|---|---|---|---|
| 1" | 4' – 6" | 4×8, 4×10, 5×8, 5×10, 6×10, 8×10, 8×16, 8×20, 10×20 | 1,307 – 8,167 lbs |
| 1 1/4" | 7' – 0" | 4×8, 4×10, 5×8, 5×10, 6×10, 8×10, 8×16, 8×20, 10×20 | 1,633 – 10,208 lbs |
Why Clear Span Matters
The maximum allowable span is one of the most important values in road plate selection. It represents the distance between supporting surfaces that the plate is designed to bridge under the referenced loading conditions.
A large road plate does not automatically permit a large unsupported trench opening. The plate still needs the required bearing and overlap beyond the opening.
Maximum Allowed Span
The listed maximum allowed span for 1-inch plate is 4 feet 6 inches under the referenced tabulated-data conditions.
Maximum Allowed Span
The listed maximum allowed span for 1 1/4-inch plate is 7 feet under the referenced tabulated-data conditions.
Road Plate Installation Best Practices
Proper installation is important because traffic loading can cause an improperly supported or unsecured plate to move, rock, or deflect.
Maintain Positive Contact
The plate should have positive contact with all supporting surfaces. Cold patch may be used to fill voids beneath the plate where appropriate.
Check the Supporting Area
The road plate chart assumes a stable trench. Stability should be determined by a Competent Person or engineer.
Secure the Plate When Required
Plates may require anchoring by pinning or welding when traffic speeds exceed 45 MPH or when the roadway slope exceeds 5%.
Control the Transition
Transition material should provide a smooth approach to the road plate and help reduce abrupt changes in roadway elevation.
Road Plate Overlap Requirements
The plate must extend beyond the excavation far enough to provide the required bearing on the supporting surface. The minimum overlap listed in the tabulated data varies by surface and traffic speed.
Minimum overlap on each side for asphalt when traffic speed is less than 45 MPH.
Minimum overlap on each side when traffic speed is greater than 45 MPH.
Minimum overlap on each side for dirt surfaces when traffic speed is less than 45 MPH.
The referenced tabulated data calls for an 18-inch minimum cold-mix asphalt transition ramp around the plate edges.
When Road Plates May Require Anchorage
Road plate movement can create a serious roadway and jobsite hazard. The applicable tabulated data identifies conditions where additional anchorage may be required.
The installation should also comply with any additional project, municipality, roadway, or engineering requirements that apply to the work.
Trench and Supporting-Surface Stability
The road plate span chart assumes a stable trench. Supporting conditions therefore matter just as much as the steel plate itself.
The Competent Person or engineer should determine whether the trench and supporting areas are suitable for the proposed installation.
If the supporting surface settles, erodes, deteriorates, or otherwise changes, the plate may no longer have the positive contact assumed by the installation.
Maintenance and Inspection
Road plates should be inspected regularly during use. The inspection should confirm that the plate remains properly positioned and that conditions around the installation have not changed.
Handling Steel Road Plates
Steel road plates are heavy. Even the smaller plate sizes in the specification chart can weigh well over 1,000 pounds, while larger plates can weigh several thousand pounds.
Lifting points should remain clear so the plates can be handled mechanically. The equipment and lifting method used on the job should be appropriate for the actual plate being moved.
What to Review Before Using a Road Plate
Before placing a steel plate over an excavation, review the complete installation rather than selecting a plate from length and width alone.
Plate Size Is Only Part of the Installation
A road plate installation should be evaluated as a complete system. Plate thickness, unsupported span, overlap, positive bearing, trench stability, anchorage, traffic speed, roadway slope, transition material, site conditions, and applicable tabulated data all affect proper use.
Need Road Plates for an Upcoming Project?
Iron Lot supplies steel road plates for utility, construction, excavation, municipal, public works, and roadway projects.
Contact us with the plate size, quantity, intended use, project location, and required timeline for current pricing, availability, shipping options, and quote information.