Millions of Americans traveled this holiday season – some stayed relatively local, while others trekked across the country to see family and friends. And, as folks who follow sustainability issues know, transportation contributes massively to global climate change and a slew of other environmental issues. But it is not always clear exactly which modes of transit are more environmentally friendly than others.

Here are some questions to consider before choosing your mode of travel for your next domestic trip. The exact details of each type of transit’s sustainability will vary greatly depending on where you live exactly, of course, but this guide will help inform your choices!

The first question to ask yourself: How far am I traveling?

For local travel, walking, biking, or taking local transit are the most sustainable ways to get around by a wide margin. Walking and biking often require zero energy use (except e-bikes, which still use a negligible amount of energy and are a very sustainable choice). Local light rail and buses are also extremely efficient, and many metropolitan areas are transitioning to running their transit using exclusively green energy (a “green” bonus).

The reality, however, is that many metropolitan areas – and particularly suburbs and rural communities – have limited bus and light rail options. The good news is that there are a growing number of more sustainable ways to travel by car.

Now, most major rideshare apps (including Lyft and Uber) offer an EV vehicle preference option, meaning that consumers can set a preference for EV rather than standard gasoline vehicles. On top of that, there are multiple local and national apps for finding folks to carpool with. If you’re wondering, what if someone else has to add a few miles to their trip to pick me up? In general, if you’re a standard commuter or traveling by car for more than just a couple of minutes, it is worth it to carpool. The environmental impact of two cars on the road is greater than just one, even if the trip of just one is slightly longer.

If you are traveling quite close to home or to a nearby city, it’s best to avoid flying, which has a massive carbon footprint for short-range trips.

Next: How much time do I have?

The amount of time you have available to travel can greatly impact which transportation choice you pick for your trip. If you have some flexibility, trains are the gold standard of sustainability, especially for regional and national travel. Train infrastructure requires significantly less space than, say, roads, and trains can hold a large number of people at a time, making their carbon footprint very low. Plus, they also tend to be one of the more comfortable ways to travel: passengers can stretch their legs, move between cars, and generally enjoy lots of personal space in their own seats. But while trains are always more sustainable than planes, they are unfortunately not always the most convenient in the United States. If you are purchasing a train ticket at the last minute, trains can be nearly as expensive as flights with longer total travel times.

This is in part because the U.S. has fallen behind other nations in their railway investments in the past half century. Particularly compared to Western Europe and East Asia, which offer increasingly affordable and frequent high-speed rail options for regional and continental travel, North America’s trains have lagged.

However, traveling by train in the U.S. will get significantly easier – and quicker – in the coming years! And it is worth keeping in mind that even if taking the train isn’t in the cards for your immediate travel plans, it may be a great option for you this time next holiday.

A giant new rail expansion package was rolled out in late 2023, which marks the largest investment in passenger rail in the country in half a century. Included in this expansion are new high-speed rail systems in California (the first in the United States!) and an expansion of existing hubs in major metro areas like Chicago and D.C. We will soon see lines along the Front Range in Colorado, connecting Oregon to British Columbia, and creating a high-speed corridor between Charlotte and Atlanta. Even the upper Midwest is seeing some benefit, with federal funding dedicated to adding a passenger line between Minneapolis and Duluth.

Finally: How many people are coming with me?

The number of people joining you on your trip may seem insignificant, but it is actually an important variable in each transportation mode’s overall carbon footprint. If you are traveling in a group or family with anywhere from 2-5 people, road trips in a car are a more sustainable option than taking a flight. This is especially true if you have a hybrid or an electric vehicle. As a bonus, packing the car for a road trip also tends to be cheaper than flying with a whole family (buying individual tickets for every single person can quickly add up).

However, if you’re traveling alone, the answer is more complicated. Depending on how far you are flying, opting to take a flight rather than driving solo in your car can reduce the overall carbon footprint of your transit. Remember, the number of people using each mode of transit matters (which explains why private jets are always unsustainable: they carry very few people at a time). So, if you’re finding that getting on the plane is the simplest and quickest option for your solo trip, don’t fret. Just remember that reducing your overall flights per year can make a big difference in your total annual environmental impact.

The bottom line: one size does not fit all!

There is no singular, perfect solution to making your travel sustainable, especially in the United States. Sometimes, how you are able to travel depends on variables totally out of your control – like the amount of time you get off of work or the infrastructure available in your neighborhood. But asking these questions can help us all maximize our transportation sustainability!