Abstract: A remote vehicle emissions measurement system comprising a radiation source, an adaptable radiation detection unit and a processing unit, characterized in that the radiation source comprises an infrared source, an ultraviolet source or a combination thereof; the radiation detection unit comprises one or more detachable and expandable detecting elements for receiving the set of predetermined wavelength bands and producing a plurality of corresponding response concurrently at any one time instant; and the processing unit comprises one or more specific software and hardware for calculating the concentrations of various gas components thereof, the relative ratio of one gas component to the others, or the absolute emission values of each of the gas components thereof in an accurate and practicable manner.