System and method for remote emission analysis of small motor vehicles

System for detecting components of the exhaust of a moving vehicle comprising: a radiation source (510) for producing radiation; a detector (510) for receiving said radiation and generating at least one signal that responds to said radiation indicative of the radiation absorption of first and second vehicle exhaust components in first and second wavelength bands; optics (531, 532, 533) to guide said radiation through more than two passes through a detection space from said source to said detector, whereby said radiation passes through the exhaust plume of a moving vehicle in said detection space, and a processor (140) that responds to the at least one signal, said processor calculating a radiation absorption rate of the first vehicle exhaust component in relation to the radiation absorption of the second exhaust component of vehicle to compensate for at least part of the dispersion of the exhaust plume; characterized in that said optics comprise a system of spherical mirrors for repeated reflection and refocusing of the radiation and, further comprising a mobile structure (390) on which the reduction source, the detector and the optics are mounted, for transport to A place of rehearsal.