On-road emission rates of carbon monoxide, nitrogen oxides, and gaseous hydrocarbon

Abstract

On-road emission rate measurements of carbon monoxide (CO), nitrogen oxides (NO/sub x/), and gaseous hydrocarbons (HC) from light-duty gasoline (spark-ignition) vehicles and from heavy-duty diesel vehicles operating at constant speed highway conditions are described. The measurements were made at the Allegheny Mountain Tunnel on the Pennsylvania Turnpike during July of 1981. Over 98,000 highway vehicle km were monitored during the study. The on-road results are compared with predictions from the EPA computer model MOBILE 2 and to other vehicle emissions studies. An effective vehicle speed was determined to account for the actual power requirements of vehicles going through the tunnel. The effective speed was then used in MOBILE 2 to predict the on-road results. CO and HC emission rates calculated by MOBILE 2 for low altitude compare within the standard deviations of the on-road measurements at the Allegheny elevation of 707 m, while predicted diesel NO/sub x/ is 2.3sigma above the on-road result and gasoline NO/sub x/ is 100% above the on-road upper limit. If the Allegheny elevation is sufficient to affect on-road emission rates, then MOBILE 2 also overpredicts CO emission rates by as much as 33%.