Almost every day, people use transport. They go to work, to the cinema, to visit friends, to be away from home. For some, transport is a major part of the job (e.g., delivery services, home care); for others, it is a major part of their leisure (e.g., road trips, cruises). This widespread use of transportation is not without environmental costs. In particular, transport is a major contributor to global greenhouse gas emissions as it has become the world‘s second-largest source of such emissions (United Nations Environment Programme, 2024). Considering this environmental challenge, the concept of ‘sustainable transport’ becomes increasingly relevant. Sustainable transport is described by the United Nations Development Programme as seeking to minimize greenhouse gas emissions and environmental impact, and at the same time considering equitable access, safety, and efficiency. It requires a combination of infrastructure, technology, policy and behavior change (United Nations Development Programme, 2025).

Behavior change is where applied psychology comes into play with the goal of understanding and shaping behavior towards more sustainability. In a joint webinar of our IAAP divisions 9 and 13, we started exploring some topics  (https://www.iaapsy.org/webinars); you will find contributions from our speakers Susan L. Handy and Margareta Friman in this issue of APAW. We decided to focus on choices related to transportation as connecting issue between our divisions because decision-making is a core topic in economic psychology. People decide on the mode of transport for specific trips (e.g., taking the train or the car), and they decide on how often to use specific transport modes over time (e.g., mixing private and public transport). They make these decisions for various reasons, including consideration of personal resources such as time, money, or effort. People face several options for more sustainable transport: collective passenger transport (transit, bus, train; carpooling), shared transport (car sharing, bike sharing), or active transport (walking, biking) (Ramanathan & O’Brien, 2023).

Deciding on how to use scarce resources (such as money, time, or energy) can take very different forms. While economics traditionally assumed that such decisions are made in a rational, utility-maximizing way, psychology has found that actual decisions deviate from these assumptions. One major insight was that decisions are not always made in a deliberative, thoughtful way. Dual-process models, most prominently the System 1 – System 2 model (Kahneman, 2013; Stanovich & West, 2000), have highlighted that in many cases, decisions occur in an automatic fashion, largely unconscious, and requiring little effort (labeled System 1, whereas System 2 is the analytic, controlled, and effortful fashion).

Habits as largely automatic responses to cues provide an easily available default (Wood & Rünger, 2016). Habits are particularly relevant for routine decisions such as how to commute to work, and have been found to be strong predictors of transport behavior (meta-analysis by Lanzini & Khan, 2017). Once car-centered habits are formed, a switch to other transport modes seems difficult (Haustein & Kroesen, 2022). However, specific events can trigger reflection and induce a habit change (see Friman et al., this issue).

Even when people make decisions in a deliberative way, actual behavior is not always aligned with their attitudes. Classical models such as the theory of planned behavior (Ajzen, 1991) have pointed to the importance of two additional factors beyond attitude: subjective norms (believing that significant others approve of a behavior) and perceived behavioral control (believing that one can perform the behavior). This theory is frequently applied, and its elements found to be major predictors of sustainable transport intentions (Lanzini & Khan, 2017). These factors seem to be relevant across a wide variety of transport modes and a wide variety of countries around the world, for example for switching to urban train services in Vietnam (Nguyen-Phuoc et al., 2025); adopting bus rapid transit in South Africa (Matubatuba & De Meyer-Heydenrych, 2022); walking in Ghana (Agyei et al., 2025); switching to electric cars in Brazil (Buranelli De Oliveira et al., 2022) or India (Deka et al., 2023), car sharing in China (Zhang & Li, 2020), or adopting various modes of sustainable transport in Italy (Mosca et al., 2024), Portugal (Nogueira et al., 2023), or Germany (Dütschke et al., 2022). Insights from these studies suggest that sustainable transport modes are more likely to be adopted when attitudes are positive, when social norms encourage their use, and when people feel in control.

A recent extension, the theory of reasoned goal pursuit (Ajzen & Kruglanski, 2019), has highlighted the importance of the motivational context. Motivation depends on the goals that are active at a specific time, and on believing that the behavior can bring one closer to the goals. One drawback of the theory of planned behavior is that it neglects why people would consider a particular behavior in the first place (Ajzen & Kruglanski, 2019). In the context of sustainable transport, an intention to reduce car use would be more likely if a goal to protect the environment is active. However, for example, a recent US poll on 2025 New Year Resolutions showed that “to do more for the environment” was only ranked 9th out of 15, mentioned by only 17% of respondents (Statista, 2024). This highlights the importance of increasing the salience of sustainability goals.

Both theories propose that actual behavioral control influences perceived behavioral control, and moderates the link between intentions and behavior. Behavioral control is strongly linked to the situational aspects that help or hinder performing a specific behavior. In the transport context, major aspects are both the physical infrastructure changes in how land-use planning guides behavior (e.g., reducing driving distances to community resources to reduce climate impacts, increasing public transport, or adding bicycle lanes) and policy regulations (e.g., increasing programs that motivate driving less while creating physical restrictions to limit driving, increase its price, or making driving harder not easier) (see Handy, this issue).

The United Nations Sustainable Development Goal 11 highlights the importance of transport for sustainable development, making it a dedicated topic (https://sdgs.un.org/topics/sustainable-transport). In 2026, the United Nations Decade of Sustainable Transport starts (https://sdgs.un.org/un-decade-sustainable-transport-2026-2035), offering many opportunities for increasing awareness and for further activities. We believe that psychology can provide valuable contributions to this topic, and we invite all readers to engage in this endeavor.

1 University of Cologne, Germany
2 University of Wisconsin-Milwaukee, United States of America

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