Passenger car equivalencies for large trucks at signalized intersections

The objective of this report was to develop passenger car equivalents (pce's) for trucks traveling straight through a level, signalized intersection based on vehicle type and position of vehicle in queue. Data were collected at three different sites and included: length of queue, classification of vehicles, and total travel time for each vehicle measured from start of green to the time the vehicle's rear axle crossed the stop line. An analytical model was developed to estimate pce values based on total travel time and vehicle type. Using this model, pce values were developed for 2 axle, single unit; 3 axle, single unit; 4 axle combination; and 5 axle combination trucks. An approximate equation was subsequently developed to predict the pce's for large vehicles based on the number of axles. This research concluded that position of vehicle in queue significantly affects the pce of the 5 axle trucks but does not affect the pce value of the smaller single unit trucks. It was further concluded that the pce value used to calculate the heavy vehicle adjustment factors in the 1985 highway capacity manual is inadequate for the large 5 axle combination trucks. Therefore, the pce values generated from this study were condensed into two values; one for light trucks and one for heavy trucks. Furthermore, the heavy vehicle adjustment factor equation was modified to analyze the effects of light and heavy trucks separately using the recommended pce values developed in this report (a).