This study estimates the costs and benefits of adopting Euro VI standards in diesel HDVs in South Africa under different timelines of fuel quality and emission standard advancements. Based on the results, also make policy recommendations that would reduce HDV emissions and improve air quality and public health in South Africa. Transportation was responsible for 7% of deaths caused by exposure to PM2.5 and ozone in 2015 in South Africa, and of these deaths, 48% are attributed to on-road diesel vehicles. Severely outdated vehicle emission standards have contributed to this deadly air pollution: the current HDV emission standards in South Africa are Euro II, first introduced in Europe more than 20 years ago and phased-out long ago there and in other major economies. South Africa has not updated its official emission standard regulations since adopting Euro II standards in 2006. Diesel engines that lack modern emission control devices produce PM2.5, soot, nitrogen oxides (NOx) and other pollutants in large quantities.