Insights from 25 Years of Measuring Real-World Vehicle Activity, Energy Use, and Emissions and Implications for the Next 25 Years

Abstract Description: As of 2022, there were over 283 million registered onroad vehicles in the United States that consumed 22 quadrillion BTU (Quads) of gasoline and diesel, and emitted 1,477 million metric tons of CO2 equivalent, as well carbon monoxide (CO), nitrogen oxides (NOx), volatile organic compounds (VOCs), and other pollutants. Internal combustion engine (ICE) vehicles comprised 87% of 2022 new light duty and commercial vehicle sales. The Energy Information Administration reference scenario is that transportation gasoline and diesel consumption will be steady at approximately 19 Quads in the decade up to 2050. Thus, there continues to be a need for development and application of methods to measure real-world activity, energy use, and emissions of such vehicles to inform individual, business, industry, community, and government decision-making. This paper focuses on the lessons learned and implications from the development, demonstration, and implementation of methods and case studies over the last 25 years at North Carolina State University for measuring real-world vehicle activity, energy use, and emissions for a wide variety of onroad vehicles, including passenger cars, passenger trucks, school buses, combination trucks, and vocational vehicles such as dump trucks, cement mixers, and refuse trucks. These methods are based on “simplified” portable emission measurement systems (PEMS). Simplified PEMS measure the exhaust concentrations of selected gases, typically CO2, CO, NO, and hydrocarbons, in combination with scanning electronic control unit data via the on-board diagnostic (OBD) data interface and collecting vehicle position and road slope data, typically with a GPS receiver augmented with an altimeter. Methodological aspects of this work have included development of standard approaches for study design, instrument preparation and calibration, instrument installation, data collection, quality assurance, data analysis, and reporting. Study design is adaptable to provide a wide range of insights and to inform a variety of decisions. Examples include assessment of the effect of transportation infrastructure, traffic operations and control, road grade, vehicle technology, fuels, drivers, ambient conditions, altitude, cold start, and others. Real-world data are also critical to evaluating the effectiveness of fuel economy and emission standards, to understanding spatial variability in emissions and implications for air quality and exposure, and to calibrating and evaluating microscale models that are using to support planning, policy and regulatory analyses. The key insights from 25 years of research will be summarized along with implications for the next 25 years leading to 2050.