Traffic loading considerations for the selection of secondary pavement structure

Many highway agencies consider only traffic volume when selecting a secondary pavement structure and others use only equivalent single axle loading (ESAL) in many cases. Traffic volume can differ significantly at the same ESAL level and ESAL can differ significantly at the same traffic volume level. The review of traffic analysis in various agencies shows that traffic volume seems to be more important in selection of a secondary pavement structure. A survey on traffic information needs for secondary pavement design demonstrates a consensus among highway professionals that both traffic volume and vehicle classification data should be considered in secondary pavement design. Based on vehicle-classification data of short counts from secondary highways in Saskatchewan, ranges of ESAL coefficients are calculated using matrixes of truck type and equivalency factor.;A traffic-loading index (TLI) is proposed for use in structure selection process to reflect traffic volume and loading situations on secondary highways. Vehicle classification counts and average daily traffic (ADT) are used to calculate the traffic loading indices. The index TLI and ADT plot is used to identify traffic level zones for corresponding pavement types. (Abstract shortened by UMI.).