OFFICIAL SITE OF THE STATE OF NEW JERSEY

Vehicle use in New Jersey is an indirect indicator of vehicle emissions, which contribute to the formation of ground level ozone. Ozone is not emitted directly into the atmosphere. Rather, it is formed by a series of reactions between nitrogen oxides and volatile organic compounds (VOCs) in the presence of sunlight. Ground level ozone is a concern because it can be harmful to breathe and can also harm sensitive vegetation during the growing season.¹  Motor vehicles are one of the largest source categories of ozone precursor emissions in New Jersey.² In addition, motor vehicles directly emit fine particulates and several air toxic pollutants such as benzene.  For additional information on ozone, please see NJDEP’s Ozone Environmental Trend Report.³

Congress passed the Clean Air Act in 1970, giving EPA the authority to regulate pollution from cars and other forms of transportation.  Since the passage of the Clean Air Act, new passenger vehicles are 98-99% cleaner for most tailpipe pollutants.⁴  The pollutants that are regulated for transportation include hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOx), and particulates.⁵  Even though vehicles today produce much less pollution per vehicle compared to the 1960s, as of 2022, transportation was still the top contributor of greenhouse gases, accounting for 28% of greenhouse gas emissions on a national scale.⁶  Increased vehicle miles traveled (VMT) per capita increases emissions of greenhouse gases and other air pollutants.⁷  The trend in VMT can be used as a surrogate to assess GHG emissions from transportation.

VMT is an indicator of vehicle use, accounting for the total miles traveled on roads and highways by motor vehicles in the state. The New Jersey Department of Transportation (DOT) estimates the peak of annual miles traveled per day occurred in 2019 at 214 million miles, dropping to 181 million miles during the beginning of the COVID-19 pandemic in 2020. The latest data in 2022 show more than 206 million miles were traveled per day (22 miles per day per person) on the state’s roadways.⁸ Diesel-fueled VMT makes up a small portion (less than 7%) of total VMT.⁹

The Highway Performance Monitoring System (HPMS) is a national highway information system that includes data on the extent, condition, performance, use, and operating characteristics of the nation’s highways. It is used to compile certified state data, including estimates of VMT, in a national database.¹⁰ These estimates are used to monitor highway use and aid the Federal Highway Administration (FHWA) in allocating federal transportation funding to individual states. The data are a reasonable approximation of vehicle travel on New Jersey’s roadways. These data do not provide estimates of other important indicators such as number of vehicle trips, the origin and destination of a trip, or the speed the vehicle is traveling during the trip. The number of trips may be more indicative of vehicle emissions than VMT because the emissions from a car are much greater for the first few minutes after start‐up, when the catalytic converter is still cold, and the engine is running with a richer mixture (higher gas to air ratio). However, trip data are not readily available. VMT data also do not consider the impacts of improved vehicle emissions control technology or electric vehicles, which has resulted in the reduced emissions of a number of pollutants. The lower emission standards of new vehicles and increased presence of electric vehicles are expected to continue the trend of reduced emissions due to the fleet turnover from older to newer vehicles. However, emissions could eventually level off and increase if VMT continues to rise.

An electric vehicle plugged in and charging (Getty Images)

The New Jersey Department of Transportation (DOT) publicly releases data on public road miles and VMT for the state. In 1975, the estimated vehicle miles traveled (VMT) in New Jersey was more than 48 billion (Figure 1).¹¹ VMT increased from 1975 through 1990 at an average rate of 681 million miles per year. From 1991 through 2007 the rate nearly doubled, increasing to over 1.2 billion miles per year, before a small decline in 2008. This change coincided with the Great Recession, a global economic downturn. During this time there was a relative peak in gasoline prices.¹² From 2008 through 2019, VMT increased at an average rate of 530 million miles per year. VMT reached a maximum of more than 78 billion miles in 2019.¹¹ In 2020, the effects of the COVID-19 pandemic sharply reduced New Jersey’s VMT estimates down to 66 billion miles, a 15% decrease from 2019 and the lowest estimate on record since 1999. Since 2020, VMT has proceeded rising again with 2022 exceeding 75 billion miles, which is nearly a 27 billion mile (55%) increase over 1975.¹¹ In contrast, New Jersey’s public roads (reported as public road miles) have increased by 5,747 miles (17%) between 1975 and 2022.¹¹

The trend of vehicle miles traveled per capita is similar to that of total VMT, but accounts for the United States Census Bureau’s estimated population data for New Jersey.^{11,13,14,15,16} Figure 2 illustrates that the annual number of VMT per person has been increasing over time in a statistically significant linear trend (Kendall Tau P-value ≤ 0.05 for 1975-2022). The U.S. Census Bureau data shows New Jersey’s estimated population increasing, with the 2022 estimate at 1.9 million (26%) more people than in 1975. Over this same time, annual vehicle miles traveled per capita is more than 1,500 miles per person (23%) greater than in 1975. The combined effect of having both a growing population and each person traveling more vehicle miles on average contributes to the greater than one and a half times increase observed in total VMT since 1975.

Figure 1. Public road miles and estimated vehicle miles traveled from 1975 to 2022 for New Jersey¹¹

Figure 2. New Jersey population and vehicle miles traveled per person from 1975 to 2022 for New Jersey^{11,13,14,15,16}

Historic trends indicate that VMT declines associated with rising fuel prices will reverse themselves once fuel prices drop. Other indicators of changing VMT trends include economic growth, affordability of auto travel, sprawl, and access to public transportation.

Even with the recent declines, the ratio of VMT to road miles remains relatively high compared to earlier years. This higher ratio of VMT to road miles partially explains why traffic congestion appears to have become increasingly problematic in the state. However, it has been argued that the solution to congestion is not to simply increase road miles, but to design effective congestion management solutions, as expanded and new highways may simply generate more traffic.¹⁷ Solutions to congestion include amending patterns of residential and commercial development to facilitate pedestrian and bicycle travel, online shopping, and telecommuting, as well as, adding to and maintaining current roadways.

Addressing congestion is one way to reduce emissions from vehicles by reducing the time spent in transit.  To further reduce emissions from transportation, increases in engine efficiency and emission reduction technology should be implemented. New Jersey has adopted and enforced regulations against excessive idling, which helps to limit unnecessary emissions (see NJDEP’s Stop the Soot webpage to learn more). Additional measures to reduce VMT and associated emissions include utilizing public transportation and carpools.  Further, electric vehicles have zero tailpipe emissions, and any emissions from power production at the power plant are typically less than those for gasoline cars.¹⁸

For more information, visit https://www.nj.gov/transportation/refdata/roadway/vmt.shtm or www.fhwa.dot.gov/environment

For more information on U.S. Greenhouse Gas Emissions, visit https://www.epa.gov/ghgemissions/inventory-us-greenhouse-gas-emissions-and-sinks

NJDEP. “Vehicle Miles Traveled.” Environmental Trends Report, NJDEP, Division of Science and Research. Last modified October 2024. Accessed [month day, year]. https://njdepwptest.net/dsr/environmental-trends/vehicle-miles-traveled/

The data used in Figures 1 and 2 are available to download here.

¹United States Environmental Protection Agency, 2024. Basic Information About Ozone. https://www.epa.gov/ground-level-ozone-pollution/ground-level-ozone-basics, Accessed 6/18/2024.

²New Jersey Department of Environmental Protection, 2023. 2022 New Jersey Air Quality Report.  https://www.nj.gov/dep/airmon/pdf/2022-nj-aq-report.pdf, Accessed 7/2/2024.

³New Jersey Department of Environmental Protection, 2021.  Ozone Environmental Trend Report.  https://njdepwptest.net/wp-content/uploads/dsr/trends-ozone.pdf, Accessed 7/2/2024.

⁴United States Environmental Protection Agency, 2024. Accomplishments and Successes of Reducing Air Pollution from Transportation in the United States. https://www.epa.gov/transportation-air-pollution-and-climate-change/accomplishments-and-successes-reducing-air, Accessed 7/2/2024.

⁵United States Environmental Protection Agency, 2024. Regulatory and Guidance Information by Topic: Air. https://www.epa.gov/regulatory-information-topic/regulatory-and-guidance-information-topic-air#transport, Accessed 7/2/2024.

⁶United States Environmental Protection Agency, 2024. Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2022. https://www.epa.gov/ghgemissions/inventory-us-greenhouse-gas-emissions-and-sinks-1990-2022, Accessed 7/2/2024.

⁷Currey, Ganson, Miller, and Fesler, 2015. Vehicle-Miles Traveled (VMT) Impacts on the Environment, Human Health, and Fiscal Health.  State Smart Transportation Initiative. https://ssti.us/wp-content/uploads/sites/1303/2015/06/Ganson-VMT-Impacts-on-the-Environment-Human-Health-and-Fiscal-Health-Working-Paper-1.pdf

⁸New Jersey Department of Transportation, 2022. Daily Vehicle Miles of Travel (1000’s). https://www.nj.gov/transportation/refdata/roadway/pdf/hpms2022/VMT_22.pdf, Accessed 7/2/2024.

⁹New Jersey Department of Transportation, 2022. Travel Activity by Vehicle Type. http://www.state.nj.us/transportation/refdata/roadway/vmt.shtm, Accessed 7/2/2024.

¹⁰US Department of Transportation, Federal Highway Administration. Highway Performance Monitoring System (HPMS). http://www.fhwa.dot.gov/policyinformation/statistics.cfm, Accessed 7/2/2024.

¹¹New Jersey Department of Transportation, 2022. Public Roadway Mileage and Vehicle Miles Traveled. https://nj.gov/transportation/refdata/roadway/vmt.shtm, Accessed 7/2/2024.

¹²Statista, 2024. Retail Price of Regular Gasoline in the United States from 1990 to 2023 (in U.S. dollars per gallon). https://www.statista.com/statistics/204740/retail-price-of-gasoline-in-the-united-states-since-1990/, Accessed 7/2/2024.

¹³U.S. Census Bureau, 1982. Estimates of the Intercensal Population of Counties 1970-1979 (E7079CO). https://www.census.gov/data/tables/time-series/demo/popest/pre-1980-county.html. Accessed 10/8/2024.

¹⁴U.S. Census Bureau, 1992. Intercensal Estimates of the Resident Population of States and Counties 1980-1989 (E8089CO). https://www.census.gov/data/tables/time-series/demo/popest/1980s-county.html. Accessed 10/8/2024.

¹⁵U.S. Census Bureau, 2020. Annual Estimates of the Resident Population for Counties in New Jersey: April 1, 2010 to July 1, 2019 (CO-EST2019-alldata). https://www.census.gov/data/tables/time-series/demo/popest/2010s-counties-total.html. Accessed 7/2/2024.

¹⁶U.S. Census Bureau, 2024. Annual Estimates of the Resident Population for Counties in New Jersey: April 1, 2020 to July 1, 2023 (CO-EST2023-POP-34). https://www.census.gov/data/tables/time-series/demo/popest/2020s-counties-total.html. Accessed 7/2/2024.

¹⁷New Jersey Department of Transportation, 2024. New Jersey FIT: Future in Transportation: The Congestion Epidemic. https://www.nj.gov/transportation/works/njfit/congestion.shtm, Accessed 7/8/2024.

¹⁸United States Environmental Protection Agency, 2024. Electric & Plug-In Hybrid Electric Vehicles. https://www.epa.gov/greenvehicles/electric-plug-hybrid-electric-vehicles, Accessed 7/8/2024.