The comprehensive understanding of the costs associated with emissions and understanding their impacts by decision-makers could help to reduce its negative effects, which is one of the main priorities for the governments in the worldwide. This knowledge would aid in establishing the policies that allow the individuals to make decisions consistent with the government and society interests in maximizing overall benefits and reducing externalities resulting from vehicle use. In the worldwide, there is pre-set goals vis-à-vis the maximum average emission. However, these goals are nearly impossible to realize without the intervention of the markets. Therefore many governments introduced the taxes to guide the personals towards reducing emissions. The purpose of this study is to explore the mediating role of driver motivations in the effect of tax-related emission factors (progressive engine size tax, progressive emissions tax, progressive vehicle age tax, and progressive vehicle kilometres travelled tax) on vehicle exhaust emissions. The study was adopted on the mixed methods approach to collect primary data, where it was focused mainly on the questionnaire and partially on the interviews. An analysis of the quantitative data was then made using Smart PLS 3.2.7. For the mediating role, the study found that the progressive taxes on engine size, vehicle age, and vehicle emissions if imposed, it will increase driver motivations to buy smaller engine size vehicle, change or maintenance old polluting vehicle or fix emission problems. The results from the interviews confirmed the results obtained by the quantitative analysis. This study contributes to the literature by presenting a systematic framework that demonstrates the underlying the Pigovian and extrinsic motivation theories. as well as achieves the theoretical and practical objectives by a clear message to practitioners and any related body of Malaysia that the progressive taxes can increase driver motivations as a strategy to reduce vehicle emissions.
