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Identifying Roadway Physical Characteristics That Contribute to Emissions Differences between Hybrid and Conventional Vehicles

Conventional vehicles and hybrid electric vehicles (HEVs) will be the dominant vehicle types in the U.S. private passenger vehicle fleet for the foreseeable future. This study used a real-time data set obtained from monitoring vehicle performance and emissions from a series of test runs from a conventional vehicle and a HEV over an 18-month period. An innovative new method of analysis allowed the assessment of different emissions rates between the two propulsion systems and the attribution of these differences to physical roadway/infrastructure characteristics. Regression and cross-classification results identify specific roadway characteristics that contribute to emissions differences between the vehicle types. Overall, the models that included maximum grade and intersection control type performed best, however, speed limit and horizontal curvature were also shown to be important. The performance differences identified in this project confirm that engine controls that are responsive to roadway characteristics are necessary.