Truck lane use is important when assessing the impact of trucks on multilane roads. A study was conducted to estimate truck lane use on tangent sections of the New Mexico rural interstate. Following review of related literature, a field study methodology was developed, data were collected, and a model was derived for estimating a truck lane distribution factor. The study determined that total vehicle volume is statistically significant in explaining truck lane use. The percent trucks of total volume also adds to the explanatory ability of the model. Three models were developed from the field data, based on three traffic volume groups. To diminish the possibility of under building a facility, precision ranges were established for the predictive ability of the models. The models were modified to account for variability in the data. An analysis was conducted of the impact of study models on pavement structural design. The study models, when compared with previous lane use estimates, typically reduced pavement thickness by 3/4 in. For all study sites the reduction in pavement thickness was between 3/4 and 1 in.
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