Traffic and environmental impacts of traffic incidents on Thessaloniki’s inner ring road

Abstract

Abstract This paper examines the traffic and the associated environmental impacts of traffic incidents with the use of the traffic microscopic simulation software Aimsun. The specific software simulates the movement of the individual vehicles and provides the option of simulating incidents at specific periods of time, thus constituting an appropriate simulation testbed. The study area includes a 14km section of the Thessaloniki’s inner ring road. The traffic volumes used in the model are of a typical weekday and they are the outputs of a macroscopic traffic assignment model properly applied in the greater city area. Traffic counts made with the use of sensors in the city road network were input in the traffic assignment model. Different scenarios of possible traffic incidents on the inner ring road in terms of location and duration were developed and evaluated using Aimsun. The impacts of defined incidents to the performance of the ring road were examined with emphasis to the near and outer area of incident position. For the evaluation process two different time periods (25 and 50 mins) and three different demand levels (low, base-case, and high) were examined. Thus, 12 different scenarios were defined and tested with the traffic microscopic simulation software. The indicators used in the evaluation process include, among others, traffic density, mean network speed, vehicle – kilometers travelled, fuel consumption, CO2 emissions etc. Results have shown that traffic speed and delays are seriously affected when incidents occur near merging or diverging areas in the inner ring road. At the same time incident duration and traffic demand deteriorated as traffic conditions increased in values.