The main purpose of the Accelerated Transportation Loading System (ATLaS) is to accelerate loading and subsequently damage to a pavement section (rather than having to wait years, as is the case with in-service pavement). This allows researchers to contrast the performance of the varying test sections.

ATLaS consists of a movable carriage that applies the load to the pavement. Each 85-foot-long section is completely tested by running the ATLaS wheel back and forth over the pavement. The ATLaS is then moved to the next section.

Tractor crawlers support the ATLaS on both ends, thereby allowing it to be positioned easily on the pavement to be tested.

The ATLaS was custom-designed and manufactured by Applied Research & Associates, Inc. in Vermont. The testing device, which cost on the order of $1.5 million, was funded by a grant from the United States Department of Transportation.

The ATLaS (the yellow machinery in this photograph) is approximately 124 feet long, 12 feet high, and 12 feet wide. It weighs around 180 kips and can load the pavement (up to 80 kips) with a single tire, dual wheel tire (typical of large trucks), or an aircraft tire.

The machine transmits a load up to 40 tons to the pavement through a hydraulic ram attached to a wheel carriage. The ATLaS wheel load can wander laterally up to three feet to simulate real-world traffic conditions.

With a 50-kip wheel one pass of the ATLaS wheel carriage at the edge of the concrete pavement is approximately equal to 1,500 equivalent single-axle loads (ESALs). One day of testing can apply up to 15 million ESALs. By comparison, a typical Chicago-area interstate undergoes approximately 500 million ESALs over a 30-year life (or 46,000 ESALS per day, on average).

A 150-foot-long movable all-weather shelter was constructed in January 2002. Throughout the pavement testing program, the shelter will be placed over the pavement and ATLaS that is being tested to protect it from the weather.

Testing is conducted under a variety of loading conditions. Some sections will receive constant loading and others, variable. Fatigue curves will be developed from this data showing how the CRCP performs under different loading conditions.

Over five years of research, including this initial project, are planned for the ATLaS. Future projects include testing a concrete overlay, an asphalt overlay, a full-depth asphalt pavement, a simulated airport runway, and simulated railroad tracks. Shown here are railroad trucks for future testing.