Behavior Nudges in Trip-Planning Apps Are Shaping How We Travel. Can They Also Make Transportation More Sustainable?
Rooted in Behavior Science, Nudges in Trip-Planning Apps Can Impact How We Choose to Move. Here’s How They Can Prioritize More Sustainable Mobility.
This spring’s Intergovernmental Panel on Climate Change report warned that climate change has already harmed people and places around the world, and that transportation, which contributes nearly a quarter of global greenhouse gas (GHG) emissions, is only worsening the crisis. Momentum around sustainable transportation is growing, especially around electric vehicles. However, even if all cars were electrified overnight with a clean electricity mix, it would not be enough to decarbonize transportation in time to limit global warming to 1.5 degrees Celsius. To hit our climate targets, it’s essential we shift away from private cars and make it easier to use more sustainable modes like public transportation, walking and bicycling.
Yet this presents a challenge in places where decades of car-centric development have cemented the idea that everyone must own and drive cars for every trip. So how do we catalyze systemic change to our transportation systems? Ultimately, we need changes in policies, regulations and investments, alongside interventions that encourage individual-level behavior change.
A growing pool of pilots and research demonstrates how to apply insights from behavioral science to encourage users to travel more sustainably. One such application is through “nudges,” interventions that steer, but don’t force, someone to change their behavior to align with a particular goal, like healthy eating or increased voter turnout. There are many examples of nudges that steer individuals toward lower-emission travel, such as transit agencies’ advertising campaigns or pricing structures to attract transit riders during off-peak times.
Designing Smarter Nudges
Today trip-planning apps guide a large share of trips, presenting an opportunity to deliver targeted, data-driven “smart nudges” to individuals. These smart nudges have the potential to be more effective than traditional nudges because they are delivered at the moment the user is making a decision, rather than directed at changing their overall attitude, and are more tailored to the individual.
So what goes into creating smart nudges for sustainable mobility? It requires bringing together multiple complex streams of information that can include the landscape of transportation options at a given place and time, the specifics of a person’s intended trip and even emissions generated by different modes. To nudge someone to use a shared electric scooter instead of ride-hailing for a specific trip, you would need to know the trip distance, if they are considering ride-hailing and if they are near an e-scooter. This nudge won’t be effective if there is no e-scooter nearby or if the trip is 25 miles long.
To pull together that information and analyze it in real time, you need extensive pre-existing digital infrastructure, much of which has already been built. Trip-planning apps like Google Maps, Transit and CityMapper allow users to plan and compare multimodal trips using services from different private mobility operators or public transit agencies. These platforms sometimes display real-time information on vehicle availability, cost and traffic, as well as varying levels of integration to pay for or book trips. Some even display the GHG emissions of trips. It is not hard to imagine these apps going a step further to incorporate personal recommendations based on characteristics like disability status, cost sensitivity and whether users are traveling with children or large items, or more nuanced environmental conditions like weather, the amount of greenery along different routes, noise and air pollution. Real-world traffic speeds enable more realistic comparisons of travel times between cars and modes that are less sensitive to traffic like walking or the subway.
Personalized trip planning and smart behavior nudges were made possible by the widespread adoption of mobility data standards like the General Transit Feed Specification (GTFS) for public transit and the General Bikeshare Feed Specification (GBFS) for bike share. These standards make it simple for trip-planning apps to incorporate information regarding transit schedules, bike availability, cost and more from many mobility operators. Other data specifications are under development to standardize information related to ride-hailing, parking and street use.
Surprise — You’re Already Being Nudged!
Delivering nudges through trip-planning apps is far from a new practice. Intentionally or not, they are already baked into user interfaces. User choices can be influenced by which trip options are displayed, the order in which they are shown, users’ default preference settings (e.g., listing by “fastest trip” or “fewest transfers”) and other elements that may not have been designed with sustainability in mind.
Additionally, many trip-planning apps include certain information for some modes but not others, and these omissions often nudge users toward car travel. It is common, for example, to display fare for transit trips but not gasoline or parking costs for private car trips, which can make car trips look, essentially, free. Similarly, trip-planning apps calculate travel times for transit to include walking to and from the transit stop, but travel times for car trips never factor in the time it takes to walk to the car, find parking and walk to the final destination, making car trips appear faster than they are. The unintended consequence is that cars can seem like the better, more convenient or more affordable option.
To illustrate, I ran an experiment: I planned a fantasy afternoon in my former home of London, during which I traveled from E5 Bakehouse, which makes my favorite sourdough bread, to see the Lubaina Himid exhibit at the Tate Modern. Below are screenshots from Google Maps, CityMapper and Transit for my trip on a Tuesday in May 2022 around 4:00 p.m. local time.
Google Maps (left) defaults to suggesting that I travel by bus and offers alternative routes by train and micromobility. Travel times by car, public transit, walking, ride-hail and bicycle are displayed in the bar at the top. Private cars, however, appear first in that bar, suggesting they may be the default option. Ride-hailing also seems to be prioritized, since it is included both as one of the five modes across the top bar and as an option within the public transit screen.
CityMapper’s (middle) top suggestions are also various mixes of public transit, but there is a matrix above that displays four travel options other than public transit (walking, biking, taxi and car share). In that matrix, walking and biking appear at the top alongside estimates of calories burned, which may appeal to health-conscious users.
Transit (right) defaults to displaying a few public transit options, ordered by earliest arrival time rather than total trip time, as well as personal bike and bike share. None of these apps estimated GHG emissions or the cost of a private car, which could include costs for fuel or parking. None offered an option to select a preference for a more sustainable trip.
The point of this experiment was not to compare different trip-planning apps on their climate-friendly nudges, but rather to demonstrate the range of approaches being used to display and prioritize trip options, and to highlight the opportunity to design user interfaces that nudge users to travel more sustainably.
The Future of Smarter Sustainable Travel Nudges
In some cities, trip-planning apps and mobility service operators are taking a more proactive, values-driven approach to incorporating smart nudges to encourage users to choose more sustainable modes.
A recent pilot by Bolt (this Bolt), which operates app-based ride-hailing and e-scooter services in Europe, used in-app nudges to shift users from ride-hailing to e-scooters. Normally e-scooters are not visible in Bolt’s app menu when booking a ride-hailing trip, but “nudged” users saw information about e-scooters in the ride-hailing menu. Results show that e-scooter mode shares among nudged users were 0.4–3% higher, a 40–200% percent increase compared to the control group. This increase indicates that simply presenting e-scooters as an option for travel made users more open to the possibility of using a mode other than a car.
In another example, Google Maps released a more fuel-efficient, “eco-friendly” routing option to reduce emissions from car travel. Meanwhile, researchers around the world are improving methodologies for designing and implementing nudges and pilots, and new apps like GoEco! and the Move Together Initiative from Moprim have emerged to help users looking to move more sustainably.
While they are not always designed with sustainability in mind, smart nudges using trip-planning apps are already shifting individual traveler behaviors. If sustainability considerations are built into how nudges are developed and deployed, then nudges could become an important approach to creating a more sustainable transportation ecosystem. Of course, behavior change alone is not enough to mitigate the worst effects of the climate crisis. We also need a more holistic systems change approach that creates an environment in which we can apply those smart nudges and other behavior science insights to promote more sustainable mobility.
This post was authored by Leah Lazer, research associate for NUMO, with contributions by Welmoed Neijmeijer from Bolt.
NUMO, the New Urban Mobility alliance, is a global organization that channels tech-based disruptions in urban transport to create joyful cities where sustainable and just mobility is the new normal. Founded in 2019 as an outgrowth of the Shared Mobility Principles for Livable Cities, NUMO convenes diverse allies and leverages the momentum of significant revolutions in mobility to target urban issues — including equity, sustainability, accessibility and labor — impacted by the shifting transportation landscape.
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