SERVICEABILITY EVALUATION OF A COMPLETE INTERSTATE HIGHWAY NETWORK

Pavement management systems (PMSs) are becoming more widely used for the efficient management of highway networks at all levels of government. PMS strategies usually provide management with two levels of information: network level and project level. Networklevel information provides broad-based data about the entire system, whereas projectlevel data are specific about construction information. The present serviceability index (PSI), or roughness of the highway, is becoming a standard tool for network evaluation. In this paper the results of an analysis of the roughness of the Interstate highway network in Pennsylvania are presented. PSI measurements were made on the network for three years (1976, 1978, 1981) and are summarized for the system as a whole, by districts, and by routes. This framework provides a picture of the change in average conditions over time and the variation in average condition from district to district and route to route. A regression analysis was performed on the data to predict conditions on the Interstates during the succeeding 5 years. An analysis was also made of the impact of betterment projects on the serviceability of the system. Results of the study indicate that the weighted mean PSI of the system has declined from 3.74 in 1976 to 3.51 in 1981. The average rate of decline annually was 0.04 between 1976 and 1978, and 0.05 between 1978 and 1981. An increase in the standard deviation suggests that the variability in conditions is increasing across the state.