Analysing the impact of traffic incidents on express road traffic flow using FREEVAL

Abstract

Traffic incidents occurring on motorways or express roads cause disruptions and deteriorate traffic conditions. The impact will differ depending on the type of incident, its duration and space blocked on the roadway and can be measured with e.g. average speed reduction, extension of travel time, time lost or overall costs of traffic disruptions. The aim of the paper is to analyse this impact, based on data from the Tri-City Ring Road (Poland). The analyses were conducted on a macroscopic level, with the use of a simulation software FREEVAL. The analysed road section was divided into homogeneous basic, merge and diverge segments. Particular traffic disturbances were introduced into individual segments, in order to represent a traffic accident or short-term road works leading to a blocked shoulder, closure of 1 lane or 2 lanes for the duration of 15 to 60 minutes. The total of 150 scenarios were analysed. The results of the analyses helped to assess how travel time and vehicle speed change depending on the location, type and duration of the traffic incident. It was found, for example, that in the case of right shoulder blockage, travel time will not change significantly (up to 3%) while the closing of 1 of 2 or 2 of 3 lanes will cause significant travel time extension (by over 500%).