According to the most recent statistics available from the EPA (year 2017) transportation was the largest and fastest-growing sector of the U.S. economy in terms of green house gas emissions. With 29% of emissions, it was ahead of electricity generation (28%) and industry (22%). Within transportation, light duty vehicle (aka mostly cars) were responsible for 59% of emissions, versus light duty trucks (23%) and aircraft (9%). Ships and Rail travel represented only 3% and 2% respectively.
The options available to consumers to reduce such transportation-related emissions are often limited by a lack of availability or practicality (i.e. public transportation in rural and suburban areas and few substitutes to aircraft for long distance travel). Nevertheless, choices exist for everyone to reduce the environmental impact of travel and transportation in general.
Commuting and short distance travel: According to the American Public Transportation Association, as of 2018, 45% of Americans had no access to public transportation. Thus, for a very large portion of the U.S. population, choosing clean and energy-efficient automobiles and light trucks is one the best ways to reduce their travel and transportation carbon footprint. Previously, fully electric cars were too pricey and their range too limited to be a practical choice for the average consumer. Now however, more affordable electric vehicles are being offered by such companies as Tesla (Model 3), GM, Volkswagen, and Japanese and Korean manufacturers. These EVs have already arrived or will soon arrive to the U.S market, and will be fully competitive against gasoline engine-driven vehicles. In the meantime, most of the largest manufacturers already offer a full range of highly efficient hybrid vehicles whose premium costs can be offset by fuel savings in as little as 2 years.
Long Distance travel. When it comes to U.S. long-distance travel, alternatives to airlines are unfortunately severely limited. If Amtrak and long-distance bus travel is not for you, two options are available: Reduce the numbers of flights you take or purchase carbon offsets. Many U.S. airlines have been offering carbon offset programs for many years already, including United, Delta and JetBlue. These companies generally work with recognized NGOs to warrant the legitimacy and efficiency of the emissions-fighting projects they fund, and the additional cost is modest, especially compared with all other airlines fees and government taxes! For a good introduction to travel carbon offsets programs, please consult the link below:
https://thepointsguy.com/guide/everything-you-need-to-know-carbon-offsetting-flights/