Influence of Truck Volume Distribution on Flexible Pavement Performance (05-1109)**
Shane Buchanan, APAC, Inc.

Accurate knowledge of truck volume and loading is essential to pavement design and performance. Underestimation of design traffic results in premature pavement failure and excessive rehabilitation costs, while overestimation results in an overly conservative pavement design that is not cost effective for owner agencies. The recently developed National Cooperative Highway Research Program (NCHRP) 1-37A Design Guide (i.e., new design guide) specifically addresses truck volume distribution via the traffic input software module. Within the module, the user has an opportunity to specify average annual daily truck traffic (AADTT), monthly and hourly truck volume distribution, vehicle class distribution, and anticipated traffic growth over the design life. Influence of these traffic factors on hot flexible pavement performance was determined with the new NCHRP design guide software for two highways in Mississippi. Results indicate AADTT, vehicle classification and traffic growth distribution most influence rutting, fatigue cracking, and longitudinal cracking distresses. Monthly and hourly truck distributions were not found to substantially influence performance.