Test Track hosts Inertial Profiler Certification Program

A profiler is a specially-equipped vehicle loaded with a system of lasers, accelerometers and other sensors often driven over highways at regular traffic speeds to collect data on smoothness. 

 

Since 2009, NCAT has provided a certification program for the Inertial Profilers. Each year, more than 40 operators and their profilers come to NCAT for their certifications, as state DOTs generally require an annual certification for operators to use their systems on state jobs.  

A “profiler” is a data collection vehicle, usually a van or truck equipped with a system of lasers, accelerometers, and other sensors to measure pavement surface characteristics as it is driven at regular traffic speeds. These data typically include smoothness, rutting, distress, and texture. 

Currently, profiler calibrations only deal with smoothness data since this is a common pay factor for many pavement construction or rehabilitation projects. Rough or uneven pavements adversely affects driver safety, fuel efficiency, ride quality, vehicle and tire condition, and pavement durability.

The NCAT Test Track, first constructed in 2000 to study the impacts of heavy traffic on asphalt pavement mixtures, also offers advantages for certification of Inertial Profilers. For its core mission, a fleet of trucks applies over a decade of typical interstate-type traffic in only two years in order to assess how the experimental pavements withstand harsh loading conditions. 

As part of the weekly operation schedule, the fleet idles on Mondays to perform maintenance on the tractor-trailers and provide safe access to the test sections for the pavement researchers.

The Alabama Department of Transportation recognized the need to ensure profiling equipment met industry standards (AASHTO R-56 and R-57) and identified the Test Track as an ideal location given the facility’s controlled access for safe testing, the opportunity to build test sections with targeted levels of roughness in the untrafficked lane, and proximity to in-state contractors.  ALDOT provided the initial funding support for the certification program, which helped NCAT acquire equipment, establish suitable pavement sections for certification, develop the training curriculum, and write the specification requirements. 

Highway departments have used segments of open roadways to serve as profiler certification sites, but doing so is less-than-ideal and makes it more challenging for profiles to remain consistent over time. While in use, the lane must be routinely closed for baseline profiles using walking profilers. Other profiler certification programs use low-volume roads or abandoned airports, but these sites are often in remote locations and may lack supporting facilities. 

To represent the range of conditions that are present in an agency’s network, locations chosen for profiler certification sites also need to offer pavements with varying levels of relatively rough and smooth pavement sections together in close proximity. 

At the NCAT Test Track, the vast majority of research test sections are located in the right lane, leaving the left lane available for profiler-specific pavements and operations. The left lane, which is not typically subjected to heavy truck passes, maintains a constant smoothness or International Roughness Index (IRI) over many years. This allows profiler operators to monitor equipment performance over time and evaluate accuracy against the baseline profile as well as historical measurements taken in previous years.  

Four sections are used to evaluate profiler accuracy and repeatability, including three dense-graded asphalt mixtures (smooth, medium-smooth, and medium-rough) and a smooth open-graded friction course. Each profiler certification section is one-tenth of a mile in length and located in the straight parts of the 1.7-mile oval track to avoid complications with the profiler’s accelerometers in the steep curves. 

Assistant Research Engineer Grant Julian is the certification coordinator and typically accepts profiler certification clients two Mondays out of each month throughout the year. 

The certification course consists of a half day of classroom training and a written exam, followed by verification testing of each of the profiler’s primary components (accelerometers, distance measuring instrument (DMI), and height sensor), followed by multiple test-runs on the certification sections at highway speeds. Profilers and operators must show a repeatability average of 92% and an accuracy average of 90% compared to the baseline profile.  

NCAT’s profiler certification program serves as the annual certification site for all profilers used on ALDOT projects and provides an evaluation compliant with AASHTO R-56 that can be used by other highway agencies. Use of the NCAT Test Track offers advantages to operators who rely on the accurate collection of data from Profilers for their management of asphalt pavements. 

For more on NCAT’s profiler certification program, contact Julian at juliagg@auburn.edu.  

 

 

For more information on NCAT’s profiler certification program, contact Grant Julian at juliagg@auburn.edu.