Carbon Emissions of Commuting from LAX to SFO

Introduction

Fig. 1: A Southwest Airlines Boeing 737-800. (Source: Wikimedia Commons)

As two of the most important economic hubs on the West Coast of the United States, millions of travelers commute between Los Angeles and San Francisco monthly. Provided that there is no existing high-speed rail connecting these two major cities, commuters are often faced with the dilemma of either driving or flying as a means of transportation. This report compares the CO₂ emissions of flying compared to driving from Los Angeles to San Francisco. The flight between these cities is widely considered to be a "short-haul" flight, as the flight duration of approximately one and a half hours is below the upper threshold of 3 hours for short-haul flights. Thus, this analysis for this route can be related closely to other "short-haul" trips, including Dallas to Houston or New York to Boston.

Mathematical Analysis

To make this comparison, the analysis will utilize a group of four travelers and focus exclusively on the travel distance from Los Angeles International Airport (LAX) to San Francisco International Airport (SFO). Any additional travel to and from the airports will be neglected for the sake of simplicity. Furthermore, the aircraft that will be analyzed will be the Boeing 737-800, shown in Fig. 1, due to its high usage by all of the major American airlines. [1] This analysis assumes a fully booked flight.

To calculate the CO₂ emissions of a car driving from Los Angeles (LAX) to San Francisco (SFO), the fuel efficiency of the car must be known to find the total amount of fuel consumed by the car. The travel distance between the two cities through Interstate 5 is approximately 615 kilometers. For a car with 8.5 kilometers per liter of fuel efficiency (approximately 20 miles per gallon), the amount of fuel consumed can be calculated as follows:

To find the CO₂ emissions from this amount of fuel consumed, the fuel consumption value will be multiplied by a factor of 44/14 to get the mass of CO₂ emitted. This multiplication factor is based on the conservation of carbon atoms. The amount of CO₂ emitted will be calculated both in total and per passenger. This calculation is shown below:

In order to calculate the amount of CO₂ emissions from a single flight from Los Angeles (LAX) to San Francisco (SFO), the fuel consumption value is first calculated. According to a paper from the Hamburg University of Applied Sciences that calculates the fuel consumption of various aircraft, the amount of fuel consumed per kilometer per seat for a Boeing 737-800 is approximately 0.0225 kilograms per kilometer per passenger. [2] This value is calculated with the knowledge that the aircraft carries a total of 162 passengers. Additionally, the flight distance from LAX to SFO is 543 kilometers. Thus, the value of the fuel consumed (in total and per passenger) for this flight is calculated below:

The corresponding amount of CO₂ emissions per passenger for this amount of fuel consumed can easily be calculated by multiplying the amount of fuel consumed per passenger by a factor of 44/14 to get the mass of CO₂ emitted per passenger. This is shown below:

Interpretation of Results

It can be seen that for a short-haul trip of approximately 600 kilometers from LAX to SFO, driving a group of four passengers produces a very similar amount of CO₂ emissions per passenger (about 40 kilograms per passenger). However, if the passenger total is decreased to just a single individual, the drive from LAX to SFO with a gasoline-powered car produces about 168 kg of CO₂ per passenger. This is more than four times the CO₂ emissions per passenger as the analogous flight. This suggests that the occupancy of the car driven is critical for this analysis. Furthermore, the CO₂ emissions per passenger of the flight assumes full capacity, which may not always be the case for unpopular flight times. Thus, the analysis is highly situational and cannot be generalized across all contexts.

Another aspect of the overall CO₂ emissions analysis that cannot be easily factored is the additional usage of additional ground transportation to reach the passengers' final destination. A large percentage of passengers will certainly utilize an additional form of transportation, such as driving, to reach their final destination. Consequentially, there will likely be significant additional CO₂ emissions to be appended to those from the flight alone.

In some countries across Europe, governmental measures have been taken to ban short-haul flights. [3] The underlying purpose behind these bans is to increase usage of rail alternatives that have been heavily developed. High-speed rail in the United States, especially from Los Angeles to San Francisco, has not yet been developed. Even with the development of such transportation methods, the usage of cars to reach the final destination must also be considered when assessing the overall reduction in CO₂ emissions.

© Ethan Yang. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.

References

[1] V. Bernardo and X. Fageda, "The Impact of New Aircraft on Carbon Emissions," Transp. Res. D 147, 104949 (2025).

[2] M. Kuhn and D. Scholz, "Fuel Consumption of the 50 Most Used Passenger Aircraft," Hochschule für Angewandte Wissenschaften Hamburg, September 2023.

[3] G. Bordeaux and A. Couto, "Rethinking Europe's Airport Ecosystem in the Age of Short-Haul Flight Bans: Winners and Losers Across Airport Tiers," Transp. Policy 175, 103878 (2026).