Development of Planning Values for Urban Freeways in Large Texas Cities (1196-1)

Using data from automatic traffic recorders (ATR) for the years 1973 to 1988 in the Texas cities of Houston, Dallas, Fort Worth, Austin, and San Antonio, this project has studied the planning parameters K and D used to determine design hour volumes. Truck percentages during peak hours have been studied using data from 24-hour manual count stations from 1984 through 1987. Variables identified and tested for signicance in predicting directional K factors (Kd) included weekday ADT per lane, degree of capacity utilization during the peak hour, employment density near the ATR station, length of peak period, and distance from the CBD. Although correlations were found using individual variables, a multivariable regression and analysis produced a highly unstable model over time. Accordingly, ranges of Kd for ranges of each variable are provided for use in determining reasonableness of preselected K and D values. Truck percentages found during peak hours are rarely above 4 percent, except on truck routes or in industrial areas.