unrealistic to predict the unclassified vehicles in terms of traffic volume and lane number at this time. Overall, vehicles under Categories 1, 2, 3, and 4 account respectively for 35%, 5%, 48%, and 12% of the total unclassified vehicles. Under clear weather conditions, the TIRTL vehicle counts agreed very well with the manual and video vehicle counts, respectively. When vehicles are classified into four categories, such as two-axle, fourtire vehicles, single unit trucks, single-trailer trucks, and multi-trailer trucks, the accuracy of vehicle classification for Category 1, including all two-axle, four-tire vehicles, was better than that for tractor trailers. WIM vehicle counts were utilized to validate the performance of TIRTL system. Unlike WIM system, the number of unclassified vehicles by TIRTL was very small.