Measurement of On-Road Tailpipe CO, NO, and Hydrocarbon Emissions Using a Portable Instrument

A portable instrument, the OEM-2100 manufactured by Clean Air Technologies International, Inc., was used to measure on-road tailpipe emissions of carbon monoxide (CO), nitric oxide (NO), hydrocarbons (HC), and carbon dioxide (CO2) on a second-by-second basis during actual driving. Engine parameters such as vehicle speed, engine rpm, engine coolant temperature, manifold absolute pressure (MAP), percent of wide open throttle, and open loop/closed loop flag were also recorded using the OEM-2100. Data have been collected for several light duty gasoline vehicles. The emissions measurement work has involved: (a) development of data collection protocols; (b) development of a study design; and (c) development of methods for analyzing the data. This paper presents the data collection protocols, examples of the data collected and example results obtained from analysis of on-road measurements. A key insight is that emissions during some modes (i.e., idling) are generally low compared to emissions during other modes (i.e., acceleration). Another finding is that emissions during a trip are substantially influenced by short-term events. The on-road emissions measurement method demonstrated in this work enables collection of real-world representative data that can be used to assist in design and management of traffic facilities, as well as for air quality monitoring, modeling, and planning purposes. A key implication of this work is that highway vehicle air quality management strategies should focus on how vehicles are driven, and not necessarily regarding how far they are driven.