VEHICLE EMISSIONS AND TRAFFIC MEASURES: EXPLORATORY ANALYSIS OF FIELD OBSERVATIONS AT SIGNALIZED ARTERIALS

ABSTRACT Understanding the relation between vehicle emissions and traffic control measures is animportant step toward reducing the potential for global warming, smog, ozone depletion, andrespiratory illness. Traffic analysts, through improved roadway design and traffic control, havethe ability to reduce vehicle emissions. However, current vehicle emissions models do not allowtraffic analysts to easily and accurately predict vehicle emissions based on commonly usedtraffic measures.The primary purpose of this exploratory research is to study the effects of traffic flow onreal-world vehicle emissions. The rates of vehicle emissions are evaluated during each “mode”of travel: acceleration, deceleration, cruise, and idle. Then, the relationship between vehicleemissions and a commonly used traffic measure, control delay, is investigated.Data for this research were collected in real-time through the use of a portable, On-boardEmission Measurement unit (OEM 2100 TM ). The OEM 2100 allows real-time, field datacollection of second-by-second measurement of tailpipe emissions (i.e., CO, HC, and NO) andengine operations (i.e., speed and engine rpm). This is the first research project deploying theOEM 2100 and differs from the majority of past emissions research in focusing on the collectionof real-world, on-road data from instrumented vehicles.A key result from this study is that vehicle emissions were found to be highest during theacceleration mode and lowest during the idling mode. Also, vehicle emissions were found to beapproximately twice as much during control delay than when not in delay. This is becauseacceleration events often occur within control delay events.KEYWORDS: Vehicle Emissions, Emissions Model, Control Delay, Signalized Arterial