THE USE OF DIFFERENT METHODOLOGIES FOR SATURATION HEADWAYS AND SATURATION FLOW RATES AT SIGNALIZED INTERSECTIONS

Capacity of signalized intersections relies on two basic parameters; allocated green time and saturation flow rate. Green time proportion depends on traffic demand, lane and phase configurations. Saturation flow rate is directly related to the roadway's environmental features and user's behavioural characteristics which significantly differ between locations. Although Highway Capacity Manual provides general guide for the estimation of saturation flow rate, its recommendations regarding particular values of design parameters, such as base saturation flow and capacity adjustment factors may not be universally applicable. On the other hand, there are a large number of methodologies for the field measurement of saturation headways. It is very important to conclude if the results of these methods are significantly different compared to the nature of the formatted queue. The present study was conducted to determine saturation flow rate for through traffic at a signalized junction in Thessaloniki. The analyses were based on two methodologies for the field measurements. Subsequently, the results of these methodologies compared to each other and to the estimated value of the saturation flow rate provided by the HCM with the use of suggested default values. The research's outputs are very important to draw conclusions for the adequate field methodology, depending on traffic conditions. Furthermore, it will reveal the differences between measured values of saturation flow rate and estimated values though the HCM. The outputs can be used in order to formulate a guide for the use of typical saturation flow rate values and therefore, capacity typical values applied to Greek urban traffic.