Recycled high-density polyethylene plastic lumber is an environmentally attractive substitute and as strong as an equivalent-sized piece of chemically treated wood. However, the original plastic lumber had an elastic modulus at least an order of magnitude less than wood. Eventually, thermoplastic composite lumber with higher elastic moduli and creep resistance was produced by incorporating reinforcing fibers within the polymer matrix. The first vehicular bridge using this reinforced thermoplastic composite lumber was built in 1998 and has paid for its higher initial material costs on a life-cycle cost basis. However, first costs are often the deciding factor in materials choice. To address that issue, a thermoplastic composite bridge was constructed using an innovative I-beam design. The result was a bridge that used less material yet could cross a 64.4 metric ton (71-ton) M-1 Abrams battle tank and still be cost competitive on a first-cost basis. Using the same design principles, two more bridges and two railway bridges have been constructed for the US Army, plus a 27.4 m (90 foot), three-span vehicular bridge was built in panels at Easter Dawyck, Scotland. This presentation describes the innovative materials, designs and performance that now make reinforced plastic lumber materials attractive, durable, and sustainable alternatives to chemically treated wood.