Development of Professional Driver Adjustment Factors for Capacity Analysis of Signalized Intersections

In the Highway Capacity Manual, various factors are provided to adjust the base saturation flow rate for the capacity analysis of signalized intersections under the prevailing conditions. There are, however, no factors to account for the possible change of capacity at signalized intersections caused by professional taxi drivers in the traffic stream. The results obtained from a study to develop professional driver adjustment factors for capacity analysis of signalized intersections are summarized. The factors were derived on the basis of the data collected in Yokohama city, Japan. The results indicated that taxi drivers had a significant impact on the saturation flow rate. When a signalized intersection was identified with a high level of taxi drivers, the saturation flow rate as well as the capacity could be increased by 20 percent, which corresponded to a professional driver adjustment factor as high as 1.20.