Common traffic data factors include the Kfactor, D-factor, and T-factor. The K-factor is the 30th highest hourly volume and is presented as a percentage of the ADT. The D-factor is the directionality of the 30th highest hourly volume of traffic. It is expressed as a percentage of the 30th highest hourly volume. The T-factor is the total percentage of single-unit trucks and multiunit combination trucks. TxDOT uses vehicle classification data and overall traffic volumes to determine the T-factor. TxDOT uses this data to develop Equivalent Single Axle Load (ESAL) calculations for pavement design. Traffic data factors are obtained from STARS II.