Together with R49, Regulation 83 addresses vehicle emissions. R83 covers emissions from all light vehicles (M1/N1) regardless of engine type and from heavier vehicles only if equipped with a gasoline engine.
Under certain circumstances, R83 or R49 can apply to light vehicle CNG/LPG engines as well as to medium passenger and commercial vehicles (M2/N2) equipped with diesel engines.
R83 also contains provisions specific to hybrid variations of the vehicles under its purview.