As we jump into the biggest travel season of the year, I wanted to focus on the amount of emissions that are created using various forms of transportation, which may be very useful for those who would like to minimize their carbon footprint during the holiday season.
There are 4 major forms of travel that will be considered here: automobile, plane, train, and bus. In order to determine the amount of carbon emissions created by each, we need a few types of information: fuel mileage (miles/gallon), how much emissions are created for each gallon of each type of fuel, and the number of people traveling. We will also need to know the type of car used when considering automobiles.
1. Fuel Mileage: Fuel mileage is going to vary considerably depending on the type of transportation, and in the case of automobiles, the type of vehicle you use. The average estimated mileage for each transportation type is given below:
Automobiles (gas): 24.9 mpg (2019 average fuel economy for new vehicles; 2020 EPA Automotive Trends Report)
Automobiles (hybrid): 50.0 mpg (represents the low end of the expected range of fuel mileage for a 2024 Toyota Prius, which can get up to 57.0 mpg.)
Automobiles (diesel): 31.7 mpg (U.S. Dept. of Energy).
Commercial Airplanes (jet fuel): 0.61 mpg (The International Council on Clean Transportation (ICCT) U.S. Domestic Airline Fuel Efficiency Ranking, 2017-2018)
Passenger Trains (diesel): 0.60 mpg (2019 Bureau of Transportation Statistics)
Commercial Bus (diesel): 6.4 mpg (2017 Motorcoach census of the U.S. and Canada by the American Bus Foundation)
2. Carbon Emissions per Gallon: The next piece of information we need is the amount of carbon emissions that are created from each gallon of fuel consumed. Estimates are given below as pounds of carbon dioxide equivalents (CO2e) per gallon of gasoline, diesel, and jet fuel (U.S. Energy Information Administration 2016 Carbon Dioxide Emissions Coefficients). Note: the term carbon dioxide equivalents means that the effects of all greenhouse gases are included.
Gasoline: 19.6 pounds of CO2e per gallon
Diesel: 22.4 pounds of CO2e per gallon
Jet Fuel: 21.1 pounds of CO2e per gallon
3. Number of People: The average number of people traveling in one car, airplane, train, or bus is needed so that you can compare your individual contribution towards carbon emissions from each type of transportation. For example, if you are in a car with one other person, you would be responsible for half of the emissions created during the trip. If you are on a plane with hundreds of people, you would be responsible for only a very small portion of the emissions created during the flight. Therefore, in order to determine whether driving or flying would create less emissions, you need to know your own individual contribution for each. The values provided below are rough averages of the number of passengers and are only provided as examples.
Commercial Airplane: ~102.4 passengers per flight (Page 6 of FAA 2024 Air Traffic by the Numbers)
Passenger Train: ~285.7 passengers per trip (Amtrak National Fact Sheet FY 2016)
Commercial Bus: ~43.7 passengers per trip (2017 Motorcoach census of the U.S. and Canada, American Bus Foundation)
Conclusions: Using the numbers above, you can see that planes and trains are by far the most inefficient in terms of how much fuel they use and emissions they create per mile, but when you consider the number of people traveling, they are much more efficient in terms of the amount of fuel used or emissions created per person (i.e., planes and trains typically contain many more people than a typical automobile).
Extra: To calculate your individual contribution towards emissions for each type of transportation, follow the steps below:
Fuel consumed: Divide the miles traveled by the fuel mileage (given above) for each type of transportation used.
Total emissons created: Multiply fuel consumed for each type of transportation by the amount of carbon emissions created per gallon (given above) for each type of transportation.
Individual emissions created: Divide total emissions created for each type of transportation by the total number of passengers (if unknown, you can guess or use the appropriate number of average passengers as given above).
Total individual emissions created: Add the results for each transportation type.
An interesting result of the above steps is that if you are traveling with more than 1 other person (a total of at least 3 passengers), your individual contribution to carbon emissions is less if you travel by car (non-hybrid) compared to by plane. If you are considering a hybrid vehicle, a plane is more efficient only if you are traveling by yourself. In contrast to all of these options, a commercial bus produces the least amount of individual emissions, though it does add considerable time to the trip.
Objective
For any upcoming trips this holiday season, attempt to determine which type of transportation would be the most environmentally-friendly in terms of your individual contribution to carbon emissions using the steps outlined above.
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