Publication Number: FHWA-HRT-04-026
Date: June 2004

The Great Pavement Profiler Round-Up

Sixty-eight road profilers. Two test tracks. Five days. The largest road profiler comparison and verification study to date was held April 4-8, 2004, at the Virginia Department of Transportation's Smart Road Facility in Blacksburg, Virginia, and the Pennsylvania Department of Transportation's road profiler testing facility in Newville, Pennsylvania. Sponsored by the Federal Highway Administration (FHWA), the profiler "round-up" study was performed by the University of Michigan Transportation Research Institute (UMTRI).

"An experiment of this size and variety was needed to improve the way people verify profilers. We also wanted to compare different types of profilers and see how reproducible profiler results are," says study director Steve Karamihas of UMTRI. "The project was also designed to increase the comfort level of States in using profiler devices," adds Mark Swanlund of FHWA. "We want to increase awareness so that using profilers becomes the standard." About 48 States are using profilers to evaluate the pavement quality of their road networks, with approximately 10 using them for construction quality control for individual projects. An additional 25 States are considering the use of profilers for construction quality control.

Road profilers use lasers and other technology to measure pavement smoothness, as calculated using indexes such as the International Roughness Index (IRI). With more highway agencies emphasizing the importance of enhancing pavement smoothness, "the payoff in using profilers is that the quality of the data is much better," says Karamihas. "You can measure what you've produced quickly on a job site, and if you see a problem with the pavement you can correct the problem before additional paving is done." Profilers provide a clearer picture of the shape of the road, while older devices, such as the California profilograph, would result in a more distorted profile that didn't exactly match the pavement. Profilers also provide a more accurate rating of how the road's smoothness would be perceived by the average driver.

In addition to comparing different types of profilers and improving methods for verifying their results, goals of the study include:

• Establishing criteria for selecting profiler verification sites;
• Studying the interaction of various profiler types with pavement surface texture; and
• Setting performance requirements for reference profilers.

The round-up featured a range of profilers, with high-speed, lightweight, low-speed, walking-speed, and reference devices tested. The measurements taken by the various profilers will be compared to reference profiles of the test roads, to check profiler accuracy, and to the results obtained by the other participating devices. Participants represented State highway agencies, FHWA, universities, manufacturers, and industry. Auburn University, for example, brought its high-speed profiler, which it has been using since 2001 for research studies. High-speed profilers mounted on trucks or vans can travel at highway speeds, with no need for traffic control. "The profiler is infinitely faster than previous methods and gives you more consistent data," says Mary Stroup-Gardiner of Auburn University.

FHWA's ultra-light profiler was built using the Segway™ Human Transporter

In Virginia, profilers were tested on the Smart Road's 2.57-km (1.6-mi) track. The track features five different 161-m long (528-ft) test sections: two with smooth asphalt and one each with rough asphalt, continuously reinforced concrete, and jointed plain concrete. The sections had downward slopes ranging from 3 percent to 6 percent. The Pennsylvania test track featured four 161-m long (528-ft) test sections: smooth concrete, rough concrete, smooth asphalt, and rough asphalt. High-speed profilers also had the option in Pennsylvania of taking measurements on three nearby road sections with live traffic.

Sixty-eight road profilers were tested at the Smart Road in Blacksburg, VA, (shown here) and the Pennsylvania Department of Transporation's road profiler testing facility in Newville, PA.

Laurin Lineman of FHWA's Federal Lands Highway Office tested the high-speed MGPS surface profiler. The MGPS surface profiler was developed from the FHWA Turner-Fairbank Highway Research Center's ROSAN texture measurement system and is now commercially available. The Federal Lands Highway Office has owned three of the profilers for 5 years and is currently in the process of implementing it as a quality assurance tool. The laser-based profiler can measure pavement texture and profiles at speeds of up to 96 km/h (60 mi/h). "We are collecting much better data with it than we did previously using the California profilograph," says Lineman. "Another advantage is that we can obtain the data a lot faster." At a cost of approximately $80,000, the profiler is more expensive than older devices such as the California profilograph, but the additional cost is offset by savings realized from not having to close traffic lanes to collect data.

Mike Upp, an engineer for the Harley-Davidson Motor Co., brought a high-speed laser profiler to the testing. The profiler is mounted on a trailer system and can be towed behind a truck or van. "We just started using the profiler this year," says Upp. "Road roughness correlates to damage, which affects our riders. We use the profiler at our own testing facilities in Alabama, Arizona, and Florida, to see what various road surfaces are like. Then we figure out how they will affect our customers. We like the trailer system because it's flexible and it's easy to ship around the country."

The Maryland State Highway Administration has two high-speed profilers that it has used for the past 4 years for quality assurance testing on new projects and for some network-wide assessments. Maryland combines the IRI data collected from the network-wide assessments with rutting and cracking data to create a Pavement Condition Index. This Index helps Maryland decide which road projects to work on. For new projects, contractors are required to report on the road's pavement smoothness. Sample quality assurance testing is then done by Maryland to check on the accuracy of the contractor's data. Contract incentives are awarded for meeting smoothness targets.

The Virginia Department of Transportation (VDOT), meanwhile, has three high-speed profilers. It uses them to measure the ride quality of new overlays and set targets for contract incentives and disincentives for pavement smoothness. VDOT also uses the profilers to collect data required for the Federal Highway Performance Monitoring System. "Virginia is also starting to use them to collect data on bridges and is looking at the profiler's ability to measure pavement texture," says Kevin McGhee of the Virginia Transportation Research Council.

FHWA tested its ultra-light, slow-speed profiler, which was built using the Segway™ Human Transporter. The device operates at about 16 km/h (10 mi/h) and performs laser measurements of the pavement. An attached computer collects the data. Another slow-speed device tested was GOMACO's new GSI® profiler, which uses sonic technology to measure the pavement. The device, which provides real-time measurements, can straddle a pavement slab to profile it and does not have to be driven on the pavement. The GSI provides smoothness readings for both wet or cured concrete and asphalt slabs. Any irregularities in the slab are identified, and their locations are recorded through the use of a distance tracking encoder. Contractors can then repair the concrete surface while it's still in the plastic state. Smoothness readings can also be seen before saw cuts are made for joints and tining or the texturing of the slab.

The GSI® profiler uses sonic technology to measure the pavement.

The data collected at the round-up will be used to test the American Association of State Highway and Transportation Officials' provisional standards, which were adopted in 2002 and published the following year. These provisional standards cover profiler use, including how to certify a profiler and how to use it on a job site. The standards also address how to incorporate pavement smoothness requirements into a paving contract. Improving the quality of pavement profile data is the goal of a new State pooled-fund study as well (see sidebar). "We want to generate a golden profiler standard against which other profilers can be measured," says Bob Orthmeyer of FHWA.

Karamihas is now evaluating the data collected at the two test tracks in April to see how repeatable the data collected from each profiler device was and how reproducible, in terms of two different devices obtaining the same result. This data evaluation will aid in determining a reference standard for profilers. All participants will receive a report about their profiler results. An overall report on the study results will also be issued later this year.

To learn more about the profiler round-up study, contact Mark Swanlund at FHWA, 202-366-1323 (email: mark.swanlund@fhwa.dot.gov), or Steve Karamihas at UMTRI, 734-936-1057 (email: stevemk@umich.edu).

Back to Articles in this Issue