Contribution of Vehicle Exhausts Gas Emissions to the Traffic Air Pollution of Selected Areas of Addis Ababa City Emission from vehicles especially automobiles are responsible for air pollution in the urban area. This study demonstrates the presence of pollutants in the air due to the contribution of vehicle exhausts gas emission on selected ambient sites kera,megenagna and urael using Model HM5000( for CO and HC) and pDR1000AN( for PM) devices. The data realize that the daily and 1, 3 and 6 hourly average concentration values of CO, HC and PM emission level directly affected by vehicle exhaust emission and distribution of old vehicles and the daily CO emission for urael ranges 17 times higher than US standard especially on Thursday and Friday, kera and megenagna get 2 times higher than US standard), for 1 hour CO emission urael get 6 times higher and kera gets 1 up to 5 times higher than US 1 hour standard. HC emission ranges for urael 6 times,for kera 5 times and 2 times for megenagna higher than the US standard. PM emission for kera and megenagna ranges little variation than the US standard especially for megenagna. Statically analysis is used in this study. The finding of this thesis realize that vehicles in the city contribute in high level of pollution totally 516 vehicles were inspected using bridge four gas analyzer 417 were gasoline vehicles CO(18.47%),HC(75.3%),CO2(60.37%) and O2(17.77%), and from 99 diesel vehicle inspection result CO(7.99 %),HC(39.59 %),CO2 (40.1%) and O2(26.14 %) emissions were observed and show that most pollutant comes from gasoline vehicles especially HC,CO2 and CO during high speed and idling of vehicles but this is not mean that diesel vehicles are not polluter there is also high O2 emission and lower HC ,CO and CO2 emission compare to gasoline one even though the samples are to small of diesel vehicles their average pollutant emission is very high and also very risky on causing ambient air pollution finally better to use gasoline vehicles than diesel one for health but for the environment they are very risky and urgent national standard for ambient air quality and vehicle exhaust emission is needed.rnKeywords: Exhaust Pollution, Gasoline engines, Diesel engines, HC emission, CO Emissions, O2 Emissions, CO2 Emissions, Particulate matters, Idle, 2500RPM, and Ambient Air Effect