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%).
Highlights
Designed to be the safest and most reliable parts of the road network, motorways and express roads are not incident-free despite their high standards
The analyses presented in the paper were made for a section of the S6 express road within the Tri-City Ring Road located in Gdansk
The main focus of the analysis was to determine how travel time changed as a result of a road incident
Summary
Designed to be the safest and most reliable parts of the road network, motorways and express roads are not incident-free despite their high standards. Road incidents both planned and unplanned, cause some disturbance and deteriorate traffic conditions by e.g. reducing average speed and road capacity [4,5,6] and by affecting travel time reliability [7,8,9]. When a bottleneck forms, vehicle stream flows are disturbed leading to the formation of a kinematic shock wave As it spreads over time and space, traffic density increases fast and average speed of traffic stream upstream of the incident location decreases. This will be the case when the volume of traffic towards the bottleneck is greater than the maximum volume that can pass across the cross-section when it is narrower. Bottleneck effects on traffic can be described by using e.g. hydrodynamic analogy [10,11], Cell Transmission Model [12], the queueing theory [13] or simulation models
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