Factors Influencing Freeway Traffic Upstream of an Incident

The authors examine the effects of incident occurrence on freeway traffic. Although the true influence of a freeway incident may not be directly observed, it may be identified using the maximum spatial extent of the disturbance induced to upstream traffic. Spatial and temporal extent is susceptible to various traffic, weather, geometry and incident specific factors. The above framework is implemented using a Multiple Indicators-Multiple Causes (MIMIC) latent variable model. Results using data from Athens, Greece indicate that the MIMIC model is able to accurately determine the influence of an incident on upstream traffic with 72% probability of producing mean square errors less than 0.05. Speed, lane volume, alignment, rainfall intensity, clearance time and whether the incident is a secondary or a primary one are among the most influential factors for assessing the anticipatory effect of incidents to traffic.