Vehicle Real-World Emissions Measurement: Methods

New Methods for Measuring Real-World Activity, Energy Use, and Emissions of Vehicles

This research developed foundational and widely-cited methodologies for measuring vehicle emissions and fuel use under real-world driving conditions using Portable Emission Measurement Systems (PEMS). A key innovation was the use of these on-board instruments to collect second-by-second data, providing the first accurate characterization of vehicle activity, fuel use, and emissions in real-world scenarios, including the effects of road grade and different driving styles. This work provided a critical empirical basis for the development of modern mobile source emissions models like MOVES.

Illustrative papers (selected examples): 

Frey, H.C., A. Unal, N.M. Rouphail, and J.D. Colyar, “On-Road Measurement of Vehicle Tailpipe Emissions Using a Portable Instrument,” Journal of Air & Waste Manage. Assoc., 53(8):992-1002 (August 2003).

Zhang, K., and H.C. Frey, “Evaluation of Response Time of a Portable System for In-Use Vehicle Tailpipe Emissions Measurements,” Environmental Science and Technology, 42(1), 221–227 (2008).

Road Grade

Zhang, K., and H.C. Frey, “Road Grade Estimation for On-Road Vehicle Emissions Modeling Using LIDAR Data,” Journal of the Air & Waste Management Association, 56(6):777-788 (June 2006).

Yazdani, B., H.C. Frey, and G.S. Sandhu, “Road Grade Measurement Using In-Vehicle, Stand-Alone GPS with Barometric Altimeter,” ASCE Journal of Transportation Engineering, 139(6):605-611 (2013).

Yazdani, B., and H.C. Frey, “Road Grade Quantification Based on Global Positioning System Data Obtained from Real-World Vehicle Fuel Use and Emission Measurements,” Atmospheric Environment, 85:179-186 (March 2014).

Procedures and Study Design

Sandhu, G.S., and H.C. Frey, “Effects of Errors on Vehicle Emission Rates from Portable Emissions Measurement Systems,” Transportation Research Record, 2340:10-19 (2013).  DOI:10.3141/2340-02.

Lee, T., and H.C. Frey, “Evaluation of Representativeness of Site-Specific Fuel-based Vehicle Emission Factors for Area-wide Average Emissions,” Environmental Science and Technology, 46(12):6867–6873 (2012).  DOI: 10.1021/es204451z.

Liu, B., and H.C. Frey, “Quantification and Application of Real-World Light Duty Vehicle Performance Envelope for Speed and Acceleration,” Transportation Research Record, 2503:128-136.  DOI: 10.3141/2503-14 (2015).

Wei, T., and H.C. Frey, “Sensitivity of light duty vehicle tailpipe emission rates from simplified portable emission measurement systems to variation in engine volumetric efficiency,” Journal of the Air & Waste Management Association, 71:9, 1127-1147 (2021). https://doi.org/10.1080/10962247.2021.1923586