Standard K Factors for Transportation Planning and Design

The K factor, defined as the proportion of annual average daily traffic occurring in an hour, has traditionally been a critical factor in highway planning and design. The standard practice is to design roadways to the 30th or 100th highest hourly volume of the year. This paper discusses the use of K factors, especially the Florida Department of Transportation’s decision to use predetermined K factors as fixed parameters based on area type and facility type. FDOT hopes that this approach will result in a more context-sensitive and cost-effective practice than the standard approach. FDOT has tested and successfully implemented the approach in one district. Based on the success of this pilot study, FDOT plans to implement the standard K factor approach throughout the state in 2012.