IMPACT OF GEOMETRY AND TRAFFIC CHARACTERISTICS ON SATURATION FLOW RATES AT SIGNALIZED INTERSECTIONS

Signalized intersections play a critical role in the motion of both urban and arterial streets. One of the basic parameters for the design and analysis of signal controlled intersections is saturation flow rate. This paper reports the estimation of saturation flow rate (SFR) considering the prevailing conditions in Egypt, at signalized intersections. Accordingly, three main objectives are stated for this study: The first one is to investigate the effect of the geometric and traffic characteristics on saturation flow rates. The second objective is to estimate a calibration factor for using US-HCM-2010 model to be suitable for the prevailing conditions in Egypt. The third objective is to develop a regression model for SFR considering intersection characteristics in Egypt.The required data for this study was collected at four signalized intersections in Shebin-Elkom city and in Tanta city using video recording technique. Geometric data and signal data were collected manually in the field. Data analysis showed that with the increase of the lane width, the saturation flow rate increases. The same conclusion can be extended to the turn-radius and vice versa with HV%. While comparing the saturation flow calculated from US-HCM-2010 with measured saturation flows, it is observed that the values aren't matching with the difference in values as 7.6%. After calibration, it can be seen that calibrated saturation flow based on US-HCM-2010 model is closer to the measured saturation flow with difference of 2.1%. Many regression models were developed for saturation flow rate considering intersection characteristics in Egypt. The best   model has R² equals 78%. This models includes 3 independent variables; %HV, lane width and lane type. The results indicated that, SFR measured using this model is closer to the field measured with a maximum difference of 1.2%. The model is valid for estimating the saturation flow rate at signalized intersections in Delta region of Egypt that have similar characteristics.