Assessing the Effect of Traffic Congestion on Greenhouse Gas Emissions

Transport activities are among the greatest contributors to greenhouse gas (GHG) emissions and despite other economic sectors the trend is still positive. Using the latest European Environment Agency guidelines in estimating vehicles emissions, the paper presents a methodology for assessing GHG emissions integrating exhaust emission factors, geographic information system (GIS) data, traffic composition surveys, and road traffic simulation. According to EU recommendation for reporting national gas inventories, the estimation of GHG emission factors based on the average speed is adopted. The computer simulation of road traffic allows for tracing individual car driving cycles and computing emissions based on average speed, mileage, fuel, and engine emission standards. The main advantage when using the computer traffic simulation is to reduce the amount of measurements which have to be performed in the field. Also the computer models have the ability to evaluate the effects of different traffic patterns (free flow, car following flow and traffic jam) and the future traffic scenarios. The carbon dioxide, methane, and nitrous oxide emissions are equated by their global warming potential. The case-study done in Carpathians outlines the way the superposition of the specific land use policy, transport network characteristics and road traffic patterns generated by the variability of human activities (the leisure-time and business tourism) can cause road congestion that increases vehicles emissions. The study presents aggregated emissions evolution by time periods and comparative values to European average levels and targets.