Effects of Traffic Congestion on Ambient Air Quality on Intersections in Addis Ababa.

No Thumbnail Available



Journal Title

Journal ISSN

Volume Title


Addis Ababa University


Nowadays, one of the major sources of greenhouse gas emission is transportation especially road transport. There are several influential factors of transport-related air pollution like road geometry, road surface type, traffic congestion, road traffic characteristics, fuel type, and environment. This study was designed to assess the effect of traffic congestion on ambient air quality at the intersection since Traffic congestion mainly occurs at the intersection due to two or more road segments meet at a place and have high traffic flow. The data provided in this study were quantitative and their sources were both primary and secondary. The primary data of the study collected using Aeroqual series 500 for carbon monoxide and sulfur dioxide, and laser PM2.5 for particular matter 2.5 and 10 air quality pollutant concentration at the roadside of the study area, and a video camera for traffic count survey. The secondary data was emission factors of different vehicles obtained from previous research papers. The data were analyzed using descriptive analysis and statistical test method. This research found out the level of traffic congestion of each selected intersection has a severe congestion level. The contribution of traffic congestion on vehicular emission as a base of steady traffic flow conditions is increased by an average value of 27-37% by car, 30-39% by minibus, 49-63% by bus, and 45-70% by truck. During congested period as a base of steady period, air pollutant concentration of CO, SO2, PM2.5 and PM 10 increased on average by 19.10%, 51.61%, 33.83% and 29.07% respectively. This study develops a regression model for air quality pollutants of CO, SO2, PM2.5, and PM10 considering different factors. From the analysis, the concentration of air pollutants increases as traffic volume, percentage of heavy vehicle, green time of the approach, approach grade increases whereas the concentration of the pollutants decreases when the lane width, wind speed increase. Therefore; traffic congestion has a negative contribution to ambient air quality.



Air quality, Emission, Traffic congestion, intersection