Percent Within Limits as Part of Federal Highway Administration’s Quality Initiatives

Federal Highway Administration’s (FHWA) dedication to construction quality continues with ongoing financial support and a research program studying statistically valid specifications. Percent within limits (PWL) is a powerful tool used to directly measure and control the average and standard deviation in a single quality measure. The risks associated with PWL specifications are quantifiable and promote the development of efficient acceptance plans. Through FHWA’s ongoing quality assurance stewardship reviews, State agency and contractor PWL perceptions and use are being documented. Perceived limitations or negative aspects specifically attributed to the PWL quality measure are typically inherent in all acceptance plans. When general quality assurance issues are removed from arguments against using PWL, the strengths associated with its use become visible.