This report describes an investigation conducted for the purpose of evaluating an experimental quantity of commercially fabricated plastic mat. The mat is a sandwich structure fabricated from glass-fabric-reinforced honeycomb core material bonded on top and bottom with epoxy adhesive to polyester-resin-impregnated, glass-fabric, laminated facings. Glass-fabric-reinforced tongue-and-groove side and end connectors are fabricated as integral parts of the panels. Laboratory and engineering traffic tests were conducted to determine various properties of the mat in an overall evaluation for comparison with the original T12 mat and with the project requirements. The service-life criteria under which the mat was tested required 200 coverages of a 25,000-lb single-wheel load with a tire-inflation pressure of 250 psi when placed on a subgrade with a California Bearing Ratio (CBR) of 4. This was more critical than the original criteria under which the T12 was tested, which specified 700 coverages of a 50,000-lb single-wheel load with tire-inflation pressures up to 200 psi when placed on a 15-CBR subgrade. (Author).