California Department of Transportation

Environmental Considerations

Trucks, freight trains, container ships, cargo planes, and freight-handling equipment are associated with environmental effects, both in terms of operation as well as the construction of related infrastructure improvements.  Particularly significant effects are associated with air quality issues related to diesel emissions. Freight movement affects the surrounding communities and contributes to greenhouse gas emissions (GHG) that contribute to climate change.  These and other impact areas are addressed under federal and state environmental laws and regulations, many of which provide processes that help avoid or reduce adverse effects. 

The Caltrans Headquarters Air Quality Branches manage the Department’s air quality analysis and transportation conformity policy; assist the district offices with regional and project-level air quality issues; consult and coordinate with state, federal, and regional air and transportation planning agencies; build and maintain air quality analysis tools and procedures; and manage research studies related to transportation air quality issues.

Community Impacts

While goods movement industries support many jobs and transport food and other products we need, communities near major highways, seaports, rail yards, border crossings, freight distribution centers, intermodal transfer facilities, and other “gateways” and “hubs” of domestic and international trade may be adversely affected in terms of air pollution, noise, congestion, health, and quality of life.  Often, the effects of transportation projects are borne by the communities residing near the freight corridor, while the benefits of goods movement are shared by a larger population at the regional, state, or national level.

Air Quality and Diesel Emissions

Goods movement has traditionally been powered by diesel engines in locomotives, marine vessels, and heavy-duty trucks, which produce tons of emissions in the form of particulate matter (PM), nitrogen oxides (NOx), and sulfur oxides (SOx).  Diesel engines emit a complex mix of pollutants, including very small carbon particles (“soot”) called diesel PM, known to contain over 40 cancer-causing substances.  Air pollution accumulates from multiple sources around ports, rail yards, and other multimodal facilities. 

Both the U.S. Environmental Protection Agency (EPA) and California Air Resources Board (ARB) classify diesel PM as a toxic air contaminant based on its potential to cause cancer, premature death, respiratory and cardiovascular effects, and other health problems.  ARB is the State agency charged with developing statewide programs and strategies to reduce the emission of smog-forming pollutants and toxics by diesel-fueled mobile sources.  ARB also actively promotes and disperses grant and incentive programs to assist trucking and freight operators comply with clean air regulations.  

Climate Change

The California Global Warming Solutions Act of 2006 (also known as Assembly Bill 32) requires that California reduce its GHG emissions to 1990 levels by 2020.  The California Air Resources Board (ARB) estimates that passenger vehicles account for most of approximately 38% of the State’s GHG emissions; however, goods movement-related transportation is also a significant contributor.  Of all transportation sources on a national scale, heavy-duty vehicles generate 19% of greenhouse gas emissions.  Information on measures to address GHG emissions can be found in ARB’s AB 32 Climate Change Scoping Plan.  The State’s adaptation strategy can be found at the California Climate Change Portal. Information regarding Caltrans climate change projects and studies is available on the Caltrans Climate Change Branch webpage.

Environmental Review

Publicly sponsored, funded, or approved projects that may potentially affect the environment must comply with a number of federal, state, and local environmental laws and regulations.  The primary federal and State environmental mandates are the federal National Environmental Policy Act (NEPA) and the California Environmental Quality Act (CEQA), respectively.  

Under NEPA and CEQA, a wide variety of potential impact areas are assessed related to the physical and natural environment, land use, cultural resources, socioeconomic effects, climate change, cumulative effects, and other topics.  Other important mandates governing freight planning include the federal and State clean air acts and environmental justice requirements.  For detailed guidance on Caltrans’s compliance with these and other environmental laws, see the Standard Environmental Reference (SER), maintained by the Division of Environmental Analysis.


Freight Planning Fact Sheets



Cameron Oakes
Acting Chief, Freight Planning
Office of Freight Planning
Division of Transportation Planning
(916) 717-1440


clean truck photo