Analysis of key parameters sensitivity and calibration accuracy of signal timing algorithm

A theoretical sensitivity analysis of total lost timeand saturated flow rate is conducted based on the methodproposed in the Highway Capacity Manual （HCM）. Inaddition, the accuracy of the timing calculation algorithmsuggested in the HCM is verified using field data from threeintersections. It is demonstrated that there is a positivecorrelation between the estimation error rates of the signalcycle length and the phase lost time. Also, the estimated valueof saturated flow rate must meet the specific requirementsunder different saturated conditions to guarantee the accuracyof the signal cycle length. However, through analysis of fielddata collected on the discharge headway in three intersections,it is also found that, if the 4th vehicle is set as the initial spotfor the stable discharge headway, as is recommended in theHCM, the error of the phase lost time will be over 40% whenthe line length is over 10 vehicles. Moreover, the calculationerror for signal cycle length is not guaranteed to fall within the15% range when the length of line is over 15 vehicles. It issuggested that, to improve the applicability of the HCMmethod, a more accurate description of the distributedregularity of the discharge headway is necessary whencalibrating key parameters.