The IJK Ride Indicator, 1976

State highway engineers realized a need for a numerical quality index and began planning for a research project of this type in 1951. The Present Serviceability Index was developed through the AASHO (now AASHTO) Road Test near Ottawa, Illinois, from 1956 to 1962.1 longitudinal profile and physical deterioration such as cracking, patching, and rut depth (for flexible pavements) were considered in deriving these Present Serviceability Index (PSI) equations

Inspector's Handbook: Well Construction, 1969

This manual is intended to serve as an aid to inspectors on well construction. Since this type of work is a noteworthy departure from that found on normal highway construction, the average inspector will be unfamiliar with the procedures and terminology employed by the contractor and his men.