Measuring the Elements of Climate Change: Truck and Auto Emissions

By Mark Tausig

Discussions of climate change often refer to phenomena such as global warming and increased greenhouse gas emissions.  Ever wonder how we measure such things?  How do we know that the global temperature has increased? How do we measure greenhouse gas amounts? What about decarbonization, tree canopies, auto and truck emissions, sea-level rise, glacier melting, and environmental justice? 

In this series, we will learn how climate change indicators are measured and how they change over time.  Reliable, ongoing measurement of these conditions is essential for monitoring climate change and promoting climate action.

Part 5: Measuring Truck and Auto Emissions

The transportation sector is one of the largest contributors to anthropogenic U.S. greenhouse gas (GHG) emissions. According to the Inventory of U.S. Greenhouse Gas Emissions and Sinks 1990–2022 (the national inventory that the U.S. prepares annually under the United Nations Framework Convention on Climate Change), transportation accounted for the largest portion (28%) of total U.S. GHG emissions in 2022. Cars, trucks, commercial aircraft, and railroads, among other sources, all contribute to transportation end-use sector emissions.

–Fast Facts: U.S. Transportation Sector GHG Emissions 1990 – 2022. May 2024, EPA-420-F-24-022)

Cars and trucks account for nearly one-fifth of all US emissions, emitting over 23 pounds of carbon dioxide and other global-warming gases for every gallon of gas. Over four pounds comes from the extraction, production, and delivery of the fuel, while the great bulk of heat-trapping emissions—about 19 pounds per gallon—comes right out of a car’s tailpipe.

–Union of Concerned Scientists.  Car Emissions and Global Warming, Published  Aug 20, 2025.

Emissions are typically measured in mass units of carbon dioxide equivalent (CO?e).  This standard unit combines different greenhouse gases based on their heat-trapping ability. For specific sources like vehicles, rates are measured in units of weight per distance traveled (e.g., grams per kilometer or pounds per mile) or parts per million (ppm) of concentration. 

Measuring car and truck emissions happens at different scales to track global climate change and local air quality. 

At the global level, top-down measurement uses national fuel production, import/export records and total sales to calculate total impact in CO2 equivalents.   Vehicle miles traveled multiplies total distance driven nationally by standard greenhouse emission factors per mile traveled.  These data are supplemented by statistical modeling systems, some direct measurement data that sample tailpipe emissions and by remote sensing devices that measure emissions by passing vehicles.

At the state and city levels, car and truck emissions are measured through mandatory annual On-Board Diagnostics (OBDII) and smoke opacity tests during vehicle inspections.  Localities also use roadside optical sensors to read exhaust gas plumes as cars and trucks drive by, portable emissions measurement systems that mount gas analyzers directly onto cars and trucks and micro-scale modeling that combines local traffic speed, vehicle age and road types to map neighborhood pollution hot spots.

Here, for example are New York State data on emissions by vehicle type.

NYS Car and Truck Emissions Breakdown (Select Years)

MMT CO2e = Million Metric Tons of carbon dioxide equivalents.

–NYS Greenhouse Gas Emissions Report, 2023.

Notice that annual emission quantities have gone UP since 1990 for both cars and trucks!  

In fact, emissions per vehicle have been reduced substantially during this period but the number of vehicles and their size have increased, leading to an overall increase in emissions. Decreasing emissions from cars and trucks requires a combination of personal driving habits, vehicle choices and, systemic shifts toward electric or alternative-fuel fleets. We are not meeting GHG reduction goals.

New York City and State are reducing vehicle emissions through pricing programs including congestion pricing, fleet electrification, stricter commercial rules, and transit investments.  Pollution from trucks has long been an issue in New York City, especially in environmental justice communities. The City has identified  initiatives to get polluting trucks off our streets, including expanding zero-emission delivery methods, installing truck charging infrastructure, and strengthening anti-idling enforcement. 

In New York City, car and truck emissions are measured through mandatory annual tests during vehicle inspections. Environmental groups and city agencies use remote sensing, traffic modeling, and community air surveys to track broader pollution levels. 

The New York City Department of Health and Mental Hygiene runs periodic community air monitoring to map local traffic and truck impacts and groups like the TRUE (True Real Urban Emissions) Initiative analyze real-world driving emissions to guide local low-emission zones and freight planning and policies.

Note that the way we measure emissions on a global, national, state or local level differ in complexity and methods.  Methods are intended to fit the objectives of planners and policy makers at each level.  Often the global measures are aggregations of local data but the aggregation enables actions that are beyond the  ability of national, state and local venues.  At the least, the measures are not incompatible.  At best, differences in what and the way GHGs or consequences of local concentrations are measured enable the development of plans and policies that address immediate climate change concerns and social and environmental equity   There is little or no controversy on the way emissions are measured at each level and there is consensus on the ways forward.  At the global level systematic changes to vehicle power (i.e., electrification) generally take precedence but at the local level issues of social justice and traffic regulation can also be considered and implemented.

Like measurements of GHGs related to global warming, building decarbonization and tree canopies, measuring car and truck emissions are well-measured and standardized.  What we do with these data are another matter.

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Mark Tausig, Ph.D., is a volunteer writer for the New York League of Conservation Voters. He is a retired Professor of Sociology, where he studied health disparities, social networks, work and mental health, international health, and population aging in low—and middle-income countries. His latest book, Population Aging in Societal Context: Evidence from Nepal, will be published by Routledge later this year (2025).