Examining the Management of Vehicular Emissions and Air Quality Standards in the Transport Sector in Oyo State

The management of vehicular emissions in Nigerian cities has gained policy urgency as air quality data increasingly document the health costs of transport pollution. This study examines the management of vehicular emissions and the application of air quality standards in the transport sector in Oyo State, South West Nigeria. A professional policy analysis and field assessment design was employed, combining a review of Nigerian and Oyo State emission regulatory frameworks with roadside emissions testing on 300 commercial and private vehicles in Ibadan and Ogbomoso, and interviews with 20 transport regulators and environmental health officers. The study evaluates emission levels against National Environmental Standards and Regulations Enforcement Agency permissible limits, enforcement mechanisms, and the condition of vehicle emission management systems. Findings reveal that over 55 percent of tested vehicles exceed permissible carbon monoxide and particulate emission levels, with ageing diesel buses and trucks showing the worst performance. Enforcement of emission standards is negligible, and mandatory periodic emissions testing for vehicles is not practised in the state. The absence of unleaded fuel and Euro-compliant fuel standards in the distribution network is identified as a structural constraint on emission reduction. Recommendations include the introduction of mandatory biennial vehicle emissions testing, the phasing in of Euro 4 fuel standards, and a voluntary clean fleet incentive programme for commercial transport operators. These findings support emission management policy development in South West Nigeria. Keywords: vehicular emissions, air quality, Oyo State, transport regulation, environmental management.