Calibration that ensures data is accurate and repeatable

"We recognize they’re very effective at what they do and they pretty much lead the pack in that regard, so that’s why we lean on them."

California Division of the State Architect

Eric France, Construction Supervisor II

55+ years of experience
PSP participants
samples shipped per year
laboratory assessments per year
accredited labs

FWD Calibration Center Operator Certification Program

The Falling Weight Deflectometer (FWD) calibration procedure ensures that pavement analysis and deflection data is accurate and repeatable.  The calibration system was developed in the early 1990s as part of the Strategic Highway Research Program’s (SHRP) Long Term Pavement Performance (LTPP) program.  Calibration center operator certification was initiated in 2004 as part of a pooled fund study by the Federal Highway Administration (FHWA).  The Cornell Local Roads Program at Cornell University developed the certification program and operated it from 2004 to 2010.  The transition of the certification program from Cornell to AASHTO re:source took place in 2010 with oversight from the FHWA.  The FHWA and Cornell Local Roads Program continue to provide oversight, guidance, and technical support for the program.

Getting Started

Interested calibration centers must submit an FWD Evaluation Request Form. Once the request has been received, AASHTO re:source staff will contact the facility’s manager to determine the date for the on-site evaluation. An announcement letter confirming the date, operators to be evaluated, and other pertinent information will be emailed to the facility. Additional details on the certification program can be found in the FWD Program Requirements.

The On-Site Evaluation

In order to maintain certification, FWD calibration center operators must be evaluated by AASHTO re:source annually. An on-site evaluation typically takes about ½ day per operator evaluated. At the beginning of the evaluation, the calibration center operator, FWD operator, and the AASHTO re:source evaluator will meet to discuss the anticipated flow of the evaluation. This is an opportunity for the FWD calibration operator and other staff to ask questions about the evaluation, the calibration protocol, and the software and equipment.

The center and operator will be evaluated for compliance to AASHTO R 32, Standard Recommended Practice for Calibrating the Load Cell and Deflection Sensors for a Falling Weight Deflectometer. Each operator will be expected to perform the calibration independently, demonstrating proficiency in use of the calibration software and equipment. In addition, the evaluator will review reference load cell calibration records to ensure that the calibration is current. At the end of the evaluation, the AASHTO re:source evaluator will review their findings with the Calibration Operator and the Facility’s Manager during a closing meeting. An Evaluation Report, documenting the evaluator’s findings, will be distributed at that time.

Preparing for an Evaluation

In order to provide the best evaluation possible, the facility must arrange for a fully-operational FWD to be available during the on-site evaluation. In addition, all required software and calibration equipment must be available and ready for use. In addition to the representative(s) from AASHTO re:source, the calibration operator(s) to be evaluated must be present for the evaluation. The calibration center must provide an additional person to operate the FWD during the calibration procedure.

After the Evaluation

After the evaluation, the center must respond to all nonconformities and observations in the Evaluation Report. All findings must be satisfactorily resolved before certification will be granted. Operators are re-evaluated annually in order to maintain certification. Certificates issued are valid for 14 months after issue date.

AASHTO re:source Team

Our evaluators are technical experts in the construction materials testing (CMT) industry and will provide you with excellent customer service. AASHTO re:source has worked closely with the Cornell Local Roads Program and FHWA to provide thorough hands-on training in FWD calibration protocol to our evaluators. AASHTO re:source actively participates in the AASHTO and ASTM standards development process and the FWD User’s Group.


AASHTO re:source prides itself on providing excellent customer service to our valued customers. Feedback regarding your on-site evaluation experience will be actively solicited during and after the evaluation. You will have the opportunity to rate the Evaluator on categories such as knowledge, communication, and punctuality. Your feedback is taken seriously and helps us improve our programs and services.