Corrugated HDPE pipe is easy to recognize due to its highly distinctive 'ribbing'. It is used for many applications such as a 'body guard' to protect sensitive and /or dangerous cables, or as drainage pipes. Another interesting application is for animal tunnels, which are placed under main roads to allow animals to cross the road safely. Single-wall corrugated HDPE pipe is used for agricultural, residential, highway culverts and recreational applications. Dual wall pipe is used for municipal storm drains and highway drainage. Due to its durability, high resistance to corrosion and chemicals, and load carrying capabilities, corrugated HDPE pipe has become the first choice for corrugated pipe, compared to concrete, clay or metal, due to the following properties: • Good balance between mechanical strength and product weight • High chemical resistance against corrosion and abrasion • Ability to withstands high loads • Light weight and flexible • Substantial cost savings during installation due to ease of handling, light weight and flexibility • Long term performance (> 50 years) HDPE corrugated pipe is environmentally friendly A study funded by the Plastics Pipe Institute, Inc. (PPI) evaluated the successful use of corrugated, high-density polyethylene (HDPE) pipe for use under heavy rail car loads with shallow cover. The test was conducted by the Transportation Technology Center, Inc. at the Facility for Accelerated Service Testing, Colorado where it operates a test bed for railroad track. The methodology of the project included repeatedly running a train consisting of 4 locomotives with eighty, 315,000 pound rail cars over 48 inch corrugated HDPE pipe with just 4 feet of cover from the top of the pipe to the bottom of the rail. In addition to the dynamic performance evaluation, the long-term impact of heavy, static loads on the pipe was assessed by parking the cars, with one set of wheels on the track directly over the same pipe for 6 weeks. The instrumented pipes performed perfectly after 96 million gross tons of heavy axle loading, with measured strains and deflections well below the material limits. The maximum measured combined deflection from construction and dynamic loading was less than 1.5% and the maximum deflection due to dynamic loads alone was 0.14%. The maximum measured tensile strains were negligible, and the maximum measured compressive strains were less than 1%. Operators noted that track ride quality was acceptable, and no track geometry maintenance was required at the conclusion of the test. The pipes were installed in two adjacent locations in a fill on the High Tonnage Loop (HTL) at FAST. The HTL is the 2.7 mile test loop where HAL tests are conducted at FAST. It is comprised of various curved, spiral, and tangent test sections. The height of the fill facilitated excavation and allowed access to both ends of the pipes after installation. There is no water flow at the fill location, and the pipes remained dry for the duration of the test. The pipes were installed 50 feet apart, center-to-center. The variable between the two sites was the composition and preparation of the backfill material. The excavations were sloped to comply with OSHA regulations. Results of Leaving Loaded Cars Parked over the Pipes for 6 Weeks One of the unknowns at the start of the test was the response of the pipes to long-term static loads. Two loaded cars at FAST were parked over the pipes for six weeks. One set of wheels from each car was directly over one of the pipes. There were slight depressions in the rails under the wheels at the end of the 6-week period. The rails rebounded when the cars were moved, and no track geometry maintenance was needed