If you’re planning a weeklong vacation and debating between a cruise voyage and a road trip, here’s something to consider: The choice could more than triple your trip’s carbon footprint.

A few years ago, we estimated that passengers on even the most efficient cruise ships emit twice as much carbon dioxide (CO₂) as someone who flies to their destination and stays in a fancy hotel. Now we’re asking a different question. What if, instead of hopping on a cruise ship, you hit the road?

The cruise option: 7-night Alaskan cruise

For both options, we modeled two travelers. The cruise is modeled as if you were aboard Royal Caribbean’s  Anthem of the Seas, a liquefied natural gas (LNG)-fueled ship capable of carrying nearly 5,000 passengers. We used a real itinerary that departs Seattle and visits Sitka, Skagway, and Juneau in Alaska, and Victoria, B.C. before returning to Seattle; the total sailing distance is  2,000 nautical miles (2,300 statute miles for you landlubbers). Based on verified 2023 data submitted under the EU Monitoring, Reporting, and Verification system, this ship emits  317 g CO₂ per passenger-nautical mile when considering tank-to-wake emissions. But these data do not include emissions from producing and transporting the fuel, or from unburned methane (“methane slip”), which is a substantial source of greenhouse gas (GHG) emissions from LNG-fueled ships.

It’s important, then, to estimate life-cycle (well-to-wake) GHG emissions in terms of CO₂ equivalent (CO₂e), and here we consider two scenarios (Table 1). The FuelEU scenario uses emission factors consistent with the European Union’s FuelEU Maritime regulation, which regulates the GHG intensity of the fuels that power ships when traveling to and from EU ports. In the FUMES scenario, well-to-tank emission factors are applied consistent with the ICCT’s Polaris shipping emissions projection model and tank-to-wake methane slip assumptions are those recommended by the Fugitive and Unburned Methane Emissions from Ships (FUMES) report. As you can see, for the 2,000 nautical mile Alaskan adventure, we estimate two travelers will emit 2.1 metric tons (FuelEU) or 2.6 metric tons (FUMES) of GHG emissions.

Table 1. Assumptions and estimated emissions from two passengers on the modeled cruise

Scenario	Well-to-tank emissions (g CO2e/MJ)	Methane slip (%)	Well-to-wake emissions  (g CO2e/passenger-nautical mile)	Total life-cycle GHG emissions   (metric tons CO2e)
FuelEU	18.5	3.1%	525	2.1
FUMES	22.8	6.0%	639	2.6

The road trip option: 7-night national parks vacation

Instead of the ship, now let’s estimate the emissions if two people rent a sport utility vehicle (SUV) in Las Vegas and set off on a 7-night, 700-mile (statute miles, people!) round-trip road trip to explore the Grand Canyon, Antelope Canyon, which is within the Lake Powell Navajo Tribal Park, and Zion National Park.

According to ICCT research, a 2024 model year SUV fueled with gasoline containing 10% corn ethanol emits a bit more than 450 g CO₂e per mile on a life-cycle basis, and a battery electric SUV emits just 130 g CO₂e per mile. Now for the hotel emissions. According to the 2024 Cornell hotel sustainability tool, a night in a 4-star hotel emits about 25 kg CO₂e (less than the 30 kg estimated in the 2021 tool). Under these assumptions, two people on this road trip would emit 490 kg of CO₂e in the gasoline SUV, including the hotels, and about 260 kg of CO₂e in the battery electric SUV and hotels combined. Emissions would be lower if staying in a less fancy hotel, of course, but we’re on vacation!

The flights for either option

Although we’re comparing emissions from a cruise trip and a road trip, it’s certainly possible that you’d have to fly to and from the starting point of each trip. To incorporate this, we assumed two people living in San Francisco who fly to and from Seattle for the cruise and to and from Las Vegas for the road trip.

Google Flights displays the average life-cycle GHG emissions per passenger for each route. (Kudos to our colleagues working on Google’s Travel Impact Model that’s behind the tool!) A round-trip flight for two people between San Francisco and Seattle would add about 510 kg of CO₂e emissions and one between San Francisco and Las Vegas would add about 350 kg of CO₂e.

The result

Taken all together, we see that even for the pair that drives a gasoline SUV, the weeklong road trip would result in less than one-third of the life-cycle GHG emissions of a weeklong cruise. With a battery electric SUV, you could take five trips for the same emissions as are associated with the cruise under the FUMES assumptions. For those curious how emissions would compare if you took an epic, 2,300-mile road trip, to align with the cruise distance, two people would emit a total of 1.7 metric tons of CO₂e if they drove a gasoline SUV or 1 metric ton of CO₂e driving the battery electric SUV, and this assumes 14 nights in hotels and keeping the flights the same. That’s still less than the cruise option.

The bigger picture

We understand the appeal of cruising, but while there are already low-emission electric cars, options for similarly low-emission summer cruises aren’t yet available. If you cruise, be careful about industry claims of low-carbon cruising, as LNG-fueled ships are expected to emit more life-cycle GHGs than those powered by today’s conventional marine fuels.

Even still, there are opportunities to reduce emissions from LNG-fueled ships. Because the European Union and the International Maritime Organization will soon put a price on methane emissions from ships through the EU Emissions Trading System and GHG penalties in the forthcoming International Maritime Organization Net-Zero Framework, there’s a business case to invest in operational strategies and technologies to minimize methane slip. However, even without counting methane emissions, cruising will still be a relatively carbon-intensive way to vacation until the industry moves to fuels with zero or near-zero life-cycle emissions. Some forward-thinking cruise operators, such as Hurtigruten, are working to offer zero-emission battery-electric cruises by 2030, but the timing, expense, and life-cycle GHG emissions of such voyages are still uncertain. Until then, we hope this analysis helps you think through your options and the emissions impacts as you take that well-deserved vacation!