Public transportation can reduce or eliminate costly car purchases, parking fees and auto insurance, and can get you there faster during rush hour (particularly with trains and subways). Also, public transportation often reduces greenhouse gases. Although the per mile greenhouse gas numbers are small, when traveling long distance the miles and greenhouse gases quickly add up. For example, the table below lists 4 hypothetical trips within the U.S., Europe, and between U.S. and Europe, and shows the 1-way and round-trip greenhouse gas emissions (GHG) in kg. One round-trip New York to Paris is over 1 metric ton (1000 Kg) and NY to Los Angeles is 80% of one ton (round-trip). In contrast, an Amtrak train ride between Boston and Washington DC would be 51 kg; half the greenhouse gases of air transport.
| Example air travel | Flight Distance (flight miles) | GHG (in Kg/mile) | 1-way (Kg GHG) | Round trip (Kg GHG) |
| New York to Los Angeles | 2445.55 | 0.164395 | 402.0 | 804.1 |
| New York to Paris | 3627.01 | 0.164395 | 596.3 | 1192.5 |
| Stockholm to Rome | 1228.35 | 0.130103 | 159.8 | 319.6 |
| Boston to Washington DC | 391.69 | 0.130103 | 51.0 | 101.9 |
The next table contrasts the efficiency of different modes of travel. Personal transportation (car, truck, motorcycle) assumes greenhouse gas per vehicle mile, whereas other transportation assumes passenger-miles. Therefore, if you load a car up with 4 family members, your passenger car GHG/mile will be ¼ of the listed rate. Also, your miles per gallon may vary from what is shown here.
| Vehicle Type | Kg GHG/Mile | Assumptions (per passenger-mile, unless stated otherwise) |
| Passenger Car | 0.307842 | Per vehicle mile: Assumes 28.9 miles per gallon |
| Light-Duty Truck | 0.407958 | Per vehicle mile |
| Motorcycle | 0.383583 | Per vehicle mile |
| Intercity Rail – NE Corridor | 0.0583395 | U.S.: Amtrak Between Boston and Washington DC. |
| Intercity Rail – Other Routes | 0.1513346 | U.S.: Amtrak |
| Intercity Rail – Nat. Avg | 0.1139466 | U.S.: Amtrak |
| Commuter Rail | 0.133983 | Between City – Suburb |
| Transit Rail | 0.093475 | Within City: Subway or Tram |
| Bus | 0.0716965 | |
| Air Travel – Short Haul (< 300 miles) | 0.2089282 | Take-off and landing require more fuel than cruising. (Bellaigue, 2023) |
| Air Travel – Medium Haul (Between 300 – 2300 miles) | 0.1301033 | To estimate distance: commercial airlines cruise at 500 – 600 miles per hour or 800-970 km/h. |
| Air Travel – Long Haul (>= 2300 miles) | 0.1643948 | Long haul rate goes up because additional fuel must be carried (Bellaigue, 2023) |
From: https://www.epa.gov/system/files/documents/2024-02/ghg-emission-factors-hub-2024.pdf
Finally, we evaluate transportation of goods, measured in greenhouse gas emissions per ton per mile. Short-ton is a U.S.-only measure, whereas one metric ton = 1000 kg (commonly used on this website). The transport order is shown in order of efficiency: rail, water, truck, air transport.
| Vehicle Type | GHG per Short-ton (U.S.) mile | GHG per Metric ton/mile |
| Rail | 0.0221801 | 0.02012 |
| Waterborne Craft | 0.0834693 | 0.07572 |
| Medium- and Heavy-Duty Truck | 0.1692875 | 0.15358 |
| Aircraft | 0.9123935 | 0.82771 |
From: https://www.epa.gov/system/files/documents/2024-02/ghg-emission-factors-hub-2024.pdf
References
EPA (2024) Emission Factors for Greenhouse Gas Inventories. Center for Corporate Climate Leadership, U.S. Environmental Protection Agency. June 5, 2024. From: https://www.epa.gov/system/files/documents/2024-02/ghg-emission-factors-hub-2024.pdf.
Christopher de Bellaigue (2023) Flying Green: On the Frontiers of Aviation. Columbia Global Reports, New York NY USA.