Vehicle, driver and atmospheric factors in light-duty vehicle particle number emissions.

PDFTech ReportUVM TRC Report # 14-006Light vehiclesPollutantsHuman factorsSpeedParticulatesExhaust gasesUpgrades (Roads)Data collectionUnited StatesUniversity of Vermont. Transportation Research CenterJackson, ErickAultman-Hall, LisaHolmen, BrittUniversity of Vermont. Transportation Research CenterNational Science Foundation (U.S.)US Transportation CollectionMade possible by the collection of on-board tailpipe emissions data, this research identifies roadand driver factors that are associated with a relatively understudied tailpipe pollutant from light-duty vehicles: ultrafine particle number emissions. High emission events (HEE) of ultrafineparticle number (PN) emissions occurred most frequently at locations with steep upgrades orlocations that required moderate to rapid accelerations (>3 mph/s). The analysis revealed thatless than 2% of the time driving was responsible for almost a third of all ultrafine particlesemitted along the designated 17-mile test route for a sample of 22 drivers. Variables identifiedin a generalized linear model as significant to PN emissions include measures of engine speed(RPM), driver behavior (speed and acceleration rates), and road geometry (grade). These factorsaccount for approximately 61% of the variability measured. Few modal emissions modelsestimate PN emissions; however, this research has revealed that the same predictor variablesused to model gas pollutants are significant predictors of PN emissions. Therefore, the additionof PN emissions estimates to existing models would require little effort if these relationshipswere developed with larger datasets. This project also documented additional challenges relatedto on-board PN data collection related to temperature, humidity, and background PNconcentrations. Finally, a large amount of the variation in light-duty PN emissions remainsunexplained, suggesting a need for more comprehensive on-board datasets, including data onparticle size distribution