Variability of traffic conditions at junction approaches in the light of non-stationary flow demands

The effects of traffic flow demand variability in time are of particular interest in the analysis of stops, queues and vehicle delays at junction approaches. The basic problems in such analyses are an identification of traffic flow variations in time and an investigation of their relation to changes in traffic conditions. The first part of the paper presents qualitative and quantitative characteristics of non-stationary traffic flow demands and their classification with respect to numerical modelling and simulation techniques as a basic study tool. A set of statistics is then used in the analysis of non-stationary flow demands, whereas studies of the effects of flow non-stationarity were done with the use of special simulation programs. The main components of the simulation models for signalised and priority-type intersections are described in the following section. Then by applying various types of arrival patterns and departure distributions described earlier, simulated measures of performance and their distributions were obtained. The last part of the paper shows the variability of traffic conditions in time and how it depends on the ratio of traffic flow saturation and on different arrival patterns.