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Lightweight Profiler Certifications

In order to assure that pavement smoothness specifications resulted in a product that provides a smooth ride for the motoring public, PennDOT began to base pavement smoothness specification on the International Roughness Index (IRI) in 2000. IRI is an expression of the rideability of the roadway, as is experienced by vehicle passengers. IRI was developed as a reference measure by The World Bank and based on a quarter-car simulation as described in NCHRP Report 228.

IRI is determined with devices known as inertial profilers or simply "profilers". Profilers are instruments used to measure road profiles. Typically, they are either high-speed profilers that travel at highway speeds, which PennDOT has been using for over a decade, or "Light Weight Profiling" (LWP) devices. An LWP is an off-road utility vehicle that can be easily used within the confines of construction projects, due to its limited size and weight, and added maneuverability. Both types of inertial profilers are usually mounted with laser sensors and computers.

PTM #428 defines the method in which to measure pavement profile and dtermine pavement ride quality for acceptance and payment using an LWP device. This PTM is provided in Appendix A. A list of acceptable models is not included. That is for two reasons: 1) The profiling technology is rapidly expanding and it is not in PennDOT's best interest to publish a PTM that may constantly need to be updated to include new LWP manufacturers and/or models; and 2) PennDOT wants to be assured that each individual LWP device is operated proficiently and provides accurate and precise results, not make blanket approvals based on type. It is with this second reason in mind, that a program has been developed to verify that all LWP devices are calibrated and operating properly.

The second aspect of the program is to certify that LWP operators are competent and capable of operating the device, as well as in collecting, analyzing, and reporting accurate results. The certification program ensures control of the use of LWP devices, promotes competence, proficiency and professionalism, and increases confidence in the test data. Operator certification is necessary because PennDOT offers no training for LWP operation. The vendors that supply LWP devices may provide training, but the extent and quality of training is beyond PennDOT's control and will vary depending on the vendor, device type, and software of each LWP device.

All LWP devices with acceptable test results will be designated with a decal to be applied by Roadway Inventory Testing Unit, and all certified LWP operators will be provided a certification card.


The LWP Calibration Verification and Operator Certification program is directed and controlled by PennDOT's Bureau of Operations (BoO), Roadway Management Division, Roadway Inventory and Testing Unit (RITU).

Each year, PennDOT will begin operations of the LWP Calibration Verification and Operator Certification program in the Spring, typically March or April. However, verifications/certifications may also be performed throughout the Summer and Fall. It is the responsibility of the LWP device owner to contact PennDOT for scheduling.

Please call 717-787-7291 or 717-783-6857 for all scheduling of LWP Certifications.

When scheduling verifications/certifications, state how many operators are to be certified during the session. Do not send additional operators to the procedure without prior PennDOT approval. If time constraints arise, PennDOT reserves the right to deny the opportunity to certify all operators during a given day. Failure to cancel a scheduled certification and/or failure to show up to a scheduled certification will result in a charge of 50% of the total certification price.