What is disclosed is a system and method for testing a motorized vehicle's exhaust emissions in a non-controlled emissions testing environment. In one embodiment, the present system comprises a toll collection structure having a sensor for obtaining information about a registered owner of a motor vehicle and about the motor vehicle itself, as the vehicle travels on a lane which passes through the structure. At least one emissions detector, which is fixed to the toll collection structure, performs an emissions test on the vehicle by analyzing an exhaust plume emitted by the vehicle. Speed/acceleration of the vehicle is also measured. In various embodiments hereof, the emissions detector comprises a combination of dispersive or non-dispersive infrared detector and a dispersive or non-dispersive ultraviolet detector. Emissions data collected is automatically compared to emissions standards and an authority is notified if that the vehicle does not meet those standards. Various embodiments are disclosed.