The Path to Sustainability: Psychological and Environmental Variables of Adolescents’ Transportation Choices

Abstract

Since adolescents are the adults of tomorrow, they are key players in increasing climate change awareness and the adoption of environmentally friendly transportation. Therefore, it is essential to understand the current and future transportation choices of adolescents in order to provide sustainability guidance to schools and communities. To this aim, a questionnaire based on the Theory of Planned Behavior was administered at school to 382 Brazilian students with an average age of 16.36 years. Regarding the results on current transportation choices, students attending public schools commute more often without adult supervision than those attending private schools and tend to travel in a more environmentally friendly manner. In terms of future transportation choices, attitudes, subjective norms, and active participation in environmental groups have a significant impact on adolescents’ intentions to choose a more sustainable mode of transport to get to work in 15 years’ time. Taking into account the socio-economic level, the results are discussed in terms of the need for awareness raising, such as education for sustainable development, and possible interventions to encourage more environmentally friendly transport choices.

1. Introduction

Air pollution is a major risk factor for noncommunicable diseases. However, in 2019, 99% of the world’s population lived in places where air quality was not in line with World Health Organization recommendations [1]. The source of air pollution and greenhouse gases is usually the same, and vehicles are an example of this [2]. The transportation sector was the largest source of emissions of carbon dioxide (the most important greenhouse gas) in 2021, accounting for 35% of total United States CO₂ emissions [3]. Brazil is one of the world’s largest emitters of greenhouse gases: while the world’s per capita CO₂ emission rate (tons CO_2eq) is 6.8, Brazil’s is 7.0 [4].

The objective of this study is related to Sustainable Development Goals, such as “good health and well-being” and “sustainable cities and communities” (SDGs; [5]). More specifically, the present study aimed to understand both the current and future (in 15 years) transport choices of Brazilian adolescents (14–18 years), focusing on environmental aspects. In relation to current transport habits, the study aimed to verify the relationship between the city’s infrastructure and the participants’ socio-economic situation. For the future, the aim was to understand whether current habits in terms of mobility choices and environmental behavior would explain the choice of more sustainable transport modes. To do so, we based our survey on the Theory of Planned Behavior factors (TPB) [6]. Based on an extensive literature review in English and Portuguese, and to the best of the authors’ knowledge, this study is innovative because it is the first to address the current and future transportation choices of adolescents in Brazil.

This study was carried out in two cities, Curitiba and União da Vitória, both located in the state of Paraná, Brazil. A medium-sized city and a large one were chosen to ensure that the sample would better represent the Brazilian reality. Curitiba has an estimated population of 1,963,726 inhabitants [7] and was chosen because it is considered the birthplace of Bus Rapid Transit (BRT) and the most sustainable city in Latin America [8]. União da Vitória, located in the countryside, has 55,033 inhabitants, and was chosen because the local population has a strong habit of using the bicycle as a mode of transport, compared to other Brazilian cities. The city is favorable for cycling because its topography is not very steep (below 10%) and the distances between the city center and the neighborhoods are short (up to 5 km) [9]. Curitiba has 1.79 inhabitants per car, while União da Vitória has 2.66, both with fewer inhabitants per car than Brazil, which has 3.68 [10]. Buses are the only form of public transport in both cities [11].

The target population was chosen because adolescents represent not only the present but are also the future adults of tomorrow. Furthermore, adolescence is an important period for shaping behavior [12], and, therefore, an important phase for implementing eco-friendly behavior interventions.

Whether a Brazilian adolescent attends a public or private school is directly related to their socio-economic situation: at higher income levels, families predominantly choose private schools [13]. This is because the quality of teaching in Brazilian private schools tends to be higher than in public schools, as they perform better in national tests [14]. While the minimum monthly wage is BRL 1320.00 (around USD 268.77 [15]), the average per capita income for families with children enrolled in private schools in Paraná is BRL 2615.99 (around USD 532.59 [13]). Another peculiarity in Brazil is that adolescents studying in public schools necessarily live nearby, as there is a law guaranteeing access to public schools in the neighborhood [16].

This paper has five main sections: the introduction, materials and methods, results, discussion, and conclusions. The introduction is divided into four subsections: Section 1.1, the determining factors of adolescents’ mobility; Section 1.2, pro-environment behavior; Section 1.3, Theory of Planned Behavior; and Section 1.4, hypotheses.

1.1. Adolescents’ Mobility Modes

Active school travel (e.g., walking and cycling) is a way to reduce traffic-related emissions [17]. The likelihood of an adolescent practicing this is directly related to the urban vitality, the proportion of pavement, and the safety facilities [18]. For example, the design of safe routes to school has an impact on the number of children walking to school [19].

The main reasons given by adolescents and their family members for not using a bicycle to get to school in Curitiba were traffic violence, robberies and thefts, and the distance between school and home. For these reasons, most parents do not allow their children to use bicycles as a mode of transport [20]. Parents are more concerned about traffic safety and crime-related safety than adolescents are. This perceived danger causes parents to discourage their children from traveling unsupervised [21]. The freedom to travel without adult supervision is called “independent mobility” [22]. In addition, among adolescents, having the support of siblings and peers for physical activity makes the built environment more attractive to engage in moderate-to-vigorous physical activity [23], and this has to do with bicycle riding or walking to get to school. Social support may be important for them to be more active [23].

Socio-economic factors can also interfere with the independent mobility of adolescents. Mothers earning lower salaries and not having a car were positively associated with greater independent mobility of adolescents when going to school. Even though interventions to change socio-demographic variables are not possible, other variables can be changed, such as making the journey to school safe by reducing traffic speeds in school zones [24] and adding more traffic lights [19].

1.2. Pro-Environment Behavior Factors

It is important to raise concern about climate change because the environment is an indicator of quality of life [25]. When adolescents act in a pro-environmental way, they do something positive for their community, but also for themselves: this behavior improves their personal and social well-being [26].

Pro-environment behavior determinants are linked to social factors (e.g., parents’ educational level, gender, family and peer influence and support) as well as the city infrastructure (e.g., neighborhood walkability) and pro-environmental education. Indeed, a recent study in Hungary showed that the higher the educational level of the parents and the better the socio-economic context of the school, the more environmentally friendly the students were [27]. Moreover, female adolescents showed more environmentally friendly behavior than male adolescents [27].

Social components also play an important role in the pro-environmental behavior of young people between the ages of 12 and 19: descriptive norms from mother, father, and best friends have a positive impact on the pro-environmental behavior of adolescents, with normative pressure from family being even stronger than that from friends [28]. For example, social support (perception of others around the user) positively predicts attitudes towards bike sharing in China [29]. Moreover, people with a long-term culture orientation (when a collectivity encourages future-oriented behavior) are more likely to engage in pro-environmental behavior, even if they lose something because of it [30].

Regarding the role of infrastructure, a study conducted in Ghana showed that there is a positive association between pro-environmental behavior and neighborhood walkability, and that knowledge about sustainability can increase the influence of pro-environmental behavior on neighborhood walkability [31]. A study in Berlin found that almost 60% of respondents would choose a car-free city center. However, this figure rises to over 90% if there is more cycle infrastructure and lower public transport fares, showing that government policies can make a difference in reducing car use and, consequently, its negative environmental and health impacts [32].

People are likely to contribute to the health of the planet through their behaviors [33]; therefore, sustainability must be taught in schools, encouraging young people to think about the future [25]. In addition, the focus of education should be more than just knowledge, because knowledge alone is not enough to engage in environmentally sound practices [34]. Interventions must address theory, but also bring experience and practice to the students. For example, an intervention in Brazil to raise students’ awareness about the topic of sustainability used reflective debates, readings, work with film and video, group dynamics, psycho-corporeal experiences, and field trips [35]. Knowledge, skills, and experience in sustaining motivation are essential for positive change [36]. Schools must indeed play their part in this process, changing the overall school culture to be environmentally friendly, e.g., replacing vending machines with water dispensers to avoid plastic waste [25]. At the same time, universities need to train future teachers to be able to implement interventions [37].

According to a federal law, in Brazil, traffic and the environment are topics that must be addressed at all levels of education [37]. Environmental education must be discussed in a transversal way, permanently. However, since many schools ignore the transversal teaching of the subject, authors suggest that the curriculum should include a subject called “Environmental Education”, so that students would be better prepared and would receive a more critical education on the topic [38].

Although studies have focused on the travel behavior in North America (e.g., Rothman et al., 2015 [19]), Europe (e.g., Mónus, 2022 [27]), and Asia (e.g., Wang et al., 2023 [18]), other regions remain underrepresented. Brazil has its own cultural, economic, and infrastructural specificities. To address this gap the present study was based on the Theory of Planned Behavior and four hypotheses were tested.

1.3. Theory of Planned Behavior (TPB)

This study was based on the TPB [6]. This theory presents four components to perform a behavior: (1) Attitudes about the target behavior; (2) Subjective norms, whether important people support (injunctive norms) or also practice (descriptive norms) the target behavior; (3) Perceived behavior control (PBC), if the person sees him/herself as capable of carrying out such an action (e.g., enough money, health, time); and (4) Intention of performing the behavior. Bamberg et al. [39] suggest that, in addition to intentions, habits and past use are relevant predictors of future behavior. Their study provides support for the use of the TPB as a theoretical framework for mode choice studies. In the present study, PBC may not have an impact on future transport choice because the participants are adolescents and may not yet perceive whether they would be able to perform the behavior.

1.4. Hypotheses

Three hypotheses were tested about current mobility behavior and one hypothesis for future mobility choices.

H1: 

Adolescents who have a cycle lane on part of the journey between their home and school use bicycles more to get to class than those who do not have a cycle lane [40,41].

H2: 

Participants who study at public schools commute more without adult supervision (independent mobility) than adolescents who study at private schools [24].

H3: 

Female students and students from private schools (with a better socio-economic background) have higher scores for Ecological Behavior [27].

H4: 

(a) The current transport habits [39], (b) attitudes and subjective norms (TPB), and (c) the current Ecological Behavior score [42] can predict the intention to choose a more sustainable mode of transport in the future, to get to work.

2. Materials and Methods

2.1. Procedure and Compliance with Ethical Standards

Data were collected in 2022 and 2023 through a printed questionnaire, applied in public (n = 7) and private (n = 4) schools. First, schools from Curitiba and União da Vitória were contacted, with a priority given to the balance between public and private schools (quota sampling). Once the institution agreed to participate, the researchers went to the classrooms, explained the study to the adolescents and handed out the consent forms. Three days later, the researchers returned to the classrooms to administer the questionnaire to the ones who brought the informed consent terms signed by their parents and by themselves (voluntary sampling). The average time taken to complete the questionnaire was 20 min. This study was previously approved by the Human Research Ethics Committee of the Human and Social Sciences Sector of the Federal University of Paraná. Adolescents did not need to identify themselves and they were not rewarded for their contribution.

2.2. Questionnaire Measures

The students’ questionnaire was elaborated by the authors. It consisted of four main sections with questions (1) about current transport habits, (2) based on the Theory of Planned Behavior (including intention, attitude, perceived behavioral control, and subjective norms), (3) about environmental behavior (Ecological Behavior Scale), and (4) on socio-demographics. The four sections are detailed below. To calculate the α presented below, all items of a given scale or subscale were selected, using the “Reliability Analysis” (Alpha).

2.2.1. Current Transport Habits

Participants were asked to specify (multiple choice) four aspects of their travel habits and current infrastructure on their way to school: (1) With whom they travelled to and from school—alone, with a younger brother/sister, parents or guardians, parents of classmates, older brother/sister, classmates, a driver (private, school van, taxi or ride-hailing car); (2) The perceived distance between home and school (close, neither close nor far, far); (3) Whether there was a cycle lane and sidewalk on this route (yes or no) and the percentage of distance covered (81 to 100%; 61 to 80%; 41 to 60%; 40% or less) in case of “yes”; (4) How often they used each mode of transport (10 modes were proposed, e.g., car, bicycle, bus, etc.) to get to school on a 4-point scale, given that never = 1, rarely = 2, sometimes = 3, and 4 = always.

2.2.2. TPB Factors About Future Transport Choice

Following the recommendations of Fishbein and Ajzen [43], preliminary interviews were carried out (free-response format) with 15 adolescents (nine females and six males; average age 15.6 years) to gather the main beliefs about modes of transport to develop TPB questions.

(a)

Intention

To measure intention, participants were asked to rate on a 4-point scale the strength (strongly disagree–strongly agree) of their intention to use each mode of transport in the future (20 modes proposed, e.g., car, bus, bicycle, motorcycle, etc.), given that strongly disagree = 1, disagree more than agree = 2, agree more than disagree = 3, and strongly agree = 4. In addition, they were asked to answer the question ‘‘In 15 years, which mode of transport do you most imagine yourself using to get to work?”. They could choose just one transport alternative.

(b)

Attitudes

Attitudes about the mode of transport they want to use in the future were assessed according to two criteria: (1) perceived advantages and disadvantages of transport choice (14 statements), e.g., “For me, the advantage of the mode of transport I would like to use to go to work is that it is comfortable”; and (2) what encourages them to make this choice (10 statements), e.g., “The desire to preserve the environment would encourage me to choose the mode of transport I intend to use in 15 years”. For all attitude-related statements, a four-point scale was used, given that strongly disagree = 1, disagree more than agree = 2, agree more than disagree = 3, and strongly agree = 4. Higher scores indicate more positive attitudes (α = 0.8). To create the variable ‘attitude’, all the items mentioned were added and then this value was divided by the number of items (N = 24).

(c)

Subjective norms

The subjective norms were divided into injunctive and descriptive norms, evaluated with one question each. The injunctive norm was formulated by asking participants “Would the people who are important to you (this could be your parents, grandparents, siblings, friends, boyfriend/girlfriend, etc.) approve of your future choice of mode of transport?”. Four response options were provided: “No one important to me would approve of my choice of a mode of transport” (1); “Some people important to me would approve of my choice of mode of transport, but others would not” (2); “Most of the people important to me would approve of my choice of mode of transport, but not all” (3); and “All the people important to me would approve of my choice of a mode of transport” (4).

To assess the descriptive norm, we asked the following question: “Compare your future choice of mode of transport with the mode of transport that the people who are important to you will use to get to work in the future (according to what you believe will happen)”. Three response options were provided: “The mode of transport I would like to be using in 15 years’ time is not the mode of transport that the people I care about will be using” (1); “The mode of transport I would like to use in 15 years’ time is the same mode of transport that some people I care about will be using, but not all of them” (2); and “The mode of transport I would like to be using in 15 years’ time is the same mode of transport that all the people who are important to me will use” (3).

(d)

Perceived behavioral control (PBC)

PBC was assessed through four statements (α = 0.7) about having enough money, skills, time, and health to choose the mode of transport they want to use in the future, given that strongly disagree = 1, disagree more than agree = 2, agree more than disagree = 3, and strongly agree = 4. For example, “In 15 years I think I’ll be able to choose the mode of transport I want to get to work, because I’ll have enough money”. To create the variable ‘PBC’, all the items mentioned were added and then this value was divided by the number of items (N = 4).

2.2.3. Ecological Behavior Scale

The “Ecological Behavior Scale” (“Escala de Comportamento Ecológico”; [44]) is a validated scale for the Brazilian population. This is a self-reported scale that measures the frequency of behaviors (never–always; 6 points; the closer to 6 the score is, the more environmentally friendly it is). This scale is composed of 29 items (α = 0.8). The factors were divided as follows: Activism-consumption (nine items; α = 0.8; refers to actions related to environmental protection that involve other people or refusal to use products considered harmful to the environment); Water and Energy Saving (twelve items; α = 0.7; refers to the rational use of natural resources, especially water and energy); Urban Cleaning (five items; α = 0.6; refers to the behavior of not throwing the garbage away in inappropriate places, keeping public spaces cleaner); and Recycling (three items; α = 0.7; refers to separating domestic waste according to its type). For example, “I separate waste by type” and “I am a volunteer worker for an environmental group”. Each subscale variable was created by adding all the items and dividing by the number of items.

2.2.4. Socio-Demographic Questions

Lastly, the students reported their age (open question), the academic year in which they were enrolled (first, second, third, or fourth), the type of school (public or private), the city where they live (Curitiba or União da Vitória), and their gender (female, male, or other).

2.3. Participants

The participants in the study comprised 382 high school students from Curitiba and União da Vitória (this sample size was expected, with a 5% margin of error and a 95% confidence level, considering a population of 62,141 high school students in the two cities). The adolescents’ characteristics are presented in

Table 1. Sample characteristics.

	Number of Participants	%
Gender 1
Female	243	64.8
Male	121	32.3
Other	11	2.9
Age
14	12	4.9
15	54	21.9
16	67	27.1
17	62	25.1
18	52	21.1
High school year
First	113	31.8
Second	85	23.9
Third	123	34.6
Fourth	34	9.6
City
Curitiba	218	57.2
União da Vitória	163	42.8
School
Public	233	63.1
Private	136	36.9
Independent mobility going to school
Yes 2	188	51.1
No 3	180	48.9
Independent mobility returning home
Yes	208	58
No	151	42
Home–school distance 4
Close	75	19.9
Neither close nor far	144	38.3
Far	157	41.8
Cycle lane between home and school
Yes	170	59.2
No	117	40.8
Percentage of cycle lane between home and school (total: 170)
81 to 100%	48	28.2
61 to 80%	82	48.2
41 to 60%	20	11.8
40% or less	16	9.4
They don’t know	4	2.4
Sidewalk between home and school
Yes	278	85.3
No	48	14.7
Percentage of sidewalk between home and school (total: 278)
81 to 100%	178	64
61 to 80%	75	27
41 to 60%	8	2.9
40% or less	6	2.1
They don’t know	11	4

¹ Participants self-identified their gender; the options were ‘male’, ‘female’, or ‘other’. ² Yes for independent mobility: alone, with younger brother/sister, with classmates. ³ No for independent mobility: with parents, a classmate’s parents, older siblings, private driver, school van, taxi, or app car. ⁴ They weren’t asked about distance in kilometers, but about their perception of the distance: (1) close; (2) neither close nor far; (3) far.

. The participants were on average 16.36 years old (standard deviation; SD = 1.18); 64.8% identified themselves as female, 57.2% were from Curitiba, and 63.1% studied in public schools. The average commuting time between home and school was 26.10 min (SD = 21.37). Although most adolescents reported having a sidewalk between their home and school (85.3%), this was not the case for all. While 59.2% of the teenagers said that there was a bicycle lane on their way to school, in most cases it did not cover the entire route.

When the participant did not answer a question, this answer was considered a missing case. The number of participants in each category does not always add up to 382 due to blank responses.

2.4. Data Analysis

The data in this study were analyzed using IBM Statistical Package for the Social Sciences Software 20. Descriptive statistics (means, standard deviations, and frequencies) as well as inferential statistical analysis, such as analysis of variance, correlation, and regression analysis, were carried out. Although there are other interesting analysis models, such as the extreme gradient boosting (XGBoost), a machine-learning technique, used, for example, to understand train usage preferences [45], this study opted for linear regression because it is one of the most classic models for prediction [46], and is suitable for the type of variable to be predicted. The following equation represents the multiple linear regression used: “Y = β₀ + β₁X₁ + β₂X₂ + β₃X₃ + β₄X₄ + β₅X₅ + β₆X₆ + β₇X₇ + β₈X₈ + β₉X₉ + β₁₀X₁₀ + β₁₁X₁₁ + ε”, where Y is the dependent variable, which in this case is the choice of more sustainable transport modes. β_n represents each continuous variable used, according to H4. Multicollinearity between predictor variables was checked using Pearson’s correlation between the variables. The highest significant correlation found was 0.395, which cannot be considered high. The independence of residuals was verified using the Durbin–Watson coefficient (1.917).

3. Results

The results are reported in four parts: (1) Descriptive analysis regarding the frequency of participants’ current mode of transport and their intention for the future; (2) City infrastructure (sidewalks and cycle lanes); (3) Independent mobility; (4) Concern about the environment.

3.1. Descriptive Analysis Regarding the Frequency of Participants’ Current Transport and Their Intention for the Future

The students answered questions about their current travel habits to get to school and their intentions for the future. The results in

Table 2. Modes of transport selected for commuting to school (current habits) and intention to commute to work (in 15 years).

Mode of Transport	% Current Habit	% Future—Intention 1	% Future—Main Intention 2
Car (gasoline or ethanol)	64.3	68.8	29.9
Walking	47.3	57.1	4.5
Bus	40.5	43.8	2.8
Bicycle	23.4	61.7	5.1
Electric car	-	78.4	27
Autonomous car	-	56	6.2
Hybrid car (combustion-powered and electric)	-	63.5	12.7
App car/Taxi	13.7	39	0.3
Van	13.4	12.2	0
Pick-up truck	13.8	37.5	2.5
Motorcycle	5.6	38.9	3.4
E-bicycle	1.5	33.7	0.3
E-scooter	1.2	24.3	0
Subway	-	38.8	2
Tram	-	27.5	0.6
Train	-	23.6	0.3
Helicopter	-	13.9	0.6
Drone	-	7.5	0.6
Airplane	-	19.4	1.1

People can use more than one mode of transport. The sign “-” means that the question was not asked. ¹ Question: “In 15 years, I want to use ___ to get to work”. Several transport options could be selected. The percentage in the Table is the percentage of frequently or always. ² Question: “In 15 years, what mode of transport do you see yourself using most to get to work?”. Only one transport option could be selected.

show a predominance of current and future car use. In addition, despite the high rate of intention to use a bicycle, few adolescents consider it the mode of transport that they most imagine themselves using.

3.2. Impact of the Infrastructure on Mobility Choice

To test Hypothesis 1, an analysis of variance was performed, verifying the differences regarding the frequency of current bicycle use (dependent variable) between two groups: (a) adolescents who reported that there were cycle lanes between their home and the school (N = 103) and (b) adolescents who reported that there was no cycle lane on this route (N = 152). There were statistically significant differences between the groups [F_{(1, 253)} = 16.00, p < 0.001]. The effect size was est.ω2 = 0.06.

Hypothesis 1a was confirmed: adolescents who have a cycle lane between home and school use the bicycle more (mean = 1.87, SD = 1.15) than adolescents without a cycle lane (mean = 1.36, SD = 0.77).

3.3. Independent Mobility

To test Hypothesis 2, a chi-square test of independence (2 × 2) was carried out, investigating whether there was an association between the type of school (public or private) and whether the adolescent commuted without adult supervision (yes or no) when going to school and returning home. A significant association was found between the type of school and independent mobility to go to (χ² (1) = 13.60, p < 0.001; φ = 0.195) and return from school (χ² (1) = 19.03, p < 0.001; φ = 0.233). These results can be seen in

Table 3. Type of school versus independent mobility.

	Independent Mobility
	Home to School			School to Home
			χ2 (df)			χ2 (df)
Type of school	Yes	No		Yes	No
Public	130	93	13.60 (1) **	147	74	19.03 (1) **
Private	52	84		56	75

** p < 0.001; χ² = chi-square; df = degree of freedom.

. Odds ratios showed that adolescents studying in public schools were 2.26 times more likely to go to school without a responsible adult than those studying in private schools, and 2.66 times more likely to return home without a responsible adult.

3.4. Concern About the Environment

Adolescents responded to the Ecological Behavior Scale. They had an average total score of 3.98 (SD = 0.73); the closer to 6, the more ecologically correct the behavior was. The average of each factor was: 2.84 (SD = 1.10) for Activism-consumption, 4.20 (SD = 0.88) for Water and Energy Saving, 5.10 (SD = 0.91) for Urban Cleaning, and 4.47 (SD = 1.45) for Recycling.

To better understand the results of the Ecological Behavior Scale and test Hypothesis 3, a one-way ANOVA was performed considering (1) gender and (2) type (public or private) of school. The results demonstrated that there were significant differences between the gender groups; bootstrapping procedures (1000 re-samples; 95% CI BCa) and Welch correction were used [Welch’s F_{(1, 361)} = 17.29, p < 0.001, est.ω2 = 0.04]. Female adolescents (M = 4.06; SD = 0.67) had higher mean scores on the Ecological Behavior Scale than male adolescents (M = 3.71; SD = 0.78). To carry out this analysis, only female and male genders were considered. There were also significant differences between the type of school [F_{(1, 366)} = 10.33, p = 0.01, est.ω2 = 0.03]. Adolescents studying in a public school (M = 4.05; SD = 0.71) had higher mean scores than those studying in a private school (M = 3.78; SD = 0.73). This partially confirms Hypothesis 3, because females and private school students were expected to have higher scores. There was no significant statistical difference between the group of Curitiba and União da Vitória residents.

In order to analyze what influences the future choice of a mode of transport according to its sustainability, we divided the modes of transport into four categories: (1) individual CO₂-emitting modes of transport (car, pick-up truck, motorcycle, etc.); (2) individual electric modes of transport (electric car, e-bike, etc.); (3) public transport (subway, bus, etc.); (4) non-CO₂-emitting/battery-free modes of transport (walking, bicycle, skateboard). To test Hypotheses 4 (a, b, and c) and to investigate the contribution of variables to estimating future choice of modes of transport, linear regression analysis (forward method) was performed.

Eleven variables were included: gender; city; age; school year; type of school (public or private); habits—frequency of walking, using the car and bicycle to travel to school (H4a); TPB factors—attitudes, injunctive norm, descriptive norm (H4b), and PBC; Ecological Behavior Scale factors (H4c). The results showed a statistically significant influence of attitudes, descriptive norms, and Activism-consumption (F_(3,291) = 17.46, p < 0.001; adjusted R² = 0.14), partially confirming Hypothesis H4b.

Table 4. Variables that predict the choice of sustainable modes of transport in the future.

Predictors	Standardized Coefficients	t	Sig.	R2
	Beta
(Constant)	-	4.063	<0.001	-
Descriptive norm 1	0.264	4.715	<0.001	0.096
Activism-consumption 2	0.171	3.170	0.002	0.119
Attitude	−0.171	−3.053	0.002	0.144

¹ Subjective norms. ² Ecological Behavior Scale.

shows the coefficients for all significant predictors and

Table 5. Non-significant variables (p > 0.05).

Predictors	Standardized Coefficients	t	Sig.
	Beta
Frequency of walking	0.089	1.647	0.101
Frequency of using the car	−0.91	−1.681	0.094
Frequency of using the bicycle	−0.93	−1.732	0.084
Injunctive norm	0.100	1.752	0.081
PBC	0.016	0.272	0.786
Water and Energy Saving	−0.073	1.227	0.221
Urban Cleaning	0.010	0.170	0.865
Recycling	0.026	0.457	0.648

presents the variables that were excluded because they did not have a statistically significant value. As can be seen, the variable that most strongly impacted the choice of sustainable modes of transport was the descriptive norm. The more sustainable the chosen mode of transport, the more similar this choice was to the choice of important people (important social referents); the worse the adolescent’s attitude towards the chosen mode of transport and the higher the score on the Activism-consumption factor (Ecological Behavior Scale).

It is important to note that if each item relating to attitude and PBC were entered separately, instead of considering the factor as a whole, the result would show a statistically significant influence of 11 variables (F_(11,283) = 30.69, p < 0.001; adjusted R² = 0.53). These variables included the descriptive norm (positive), PBC related to having money (negative), the habit of cycling to get to school (negative), recycling (positive), and seven items related to advantages: carrying things or people (negative); protecting the environment (positive); being safe from sexual harassment (negative); physical exercise (positive); not getting tired (negative); financial cost (positive); speed (negative).

4. Discussion

The present study aimed to understand the current and future (in 15 years) transport choices of Brazilian high school students. From the point of view of traffic-related pollution, understanding adolescents’ transport choices is important not only because they are currently commuting to school, but also because they are likely to be future workers commuting daily. The results show high levels of current and future car use. This reality is worrying for the environment and requires intervention. To support this, it is essential to understand the determinants of the adolescents’ transport choices.

Regarding the current mode of transport to school by teenagers, Hypothesis 1 was confirmed, i.e., choosing to use a bicycle is related to the city’s infrastructure: teenagers who find cycle lanes on their route to school use bicycles more often. This finding is in line with previous studies on infrastructure [32,40,41] and is also in line with results about the relationship between practicing active school travel and traffic safety [18,20]. The practice of active mobility is very important to avoid CO₂ emissions [17]. Governments must therefore invest in infrastructure projects that include sidewalks and cycle lanes to encourage families to let their children cycle and walk to school.

Given that adolescents under 18 years are not allowed to drive in Brazil, independent mobility for teenagers is necessarily environmentally friendly. Hypothesis 2 was confirmed: public school students practice independent mobility more than private school students, a finding that agrees with Rodríguez-Rodríguez et al. [24]. Two explanations for this could be (1) the socio-economic level [24] and (2) proximity to school [16]. Because of this, parents who prefer to enroll their children in private schools could prioritize the ones close to their homes whenever possible, encouraging the use of micro mobility [20] and, consequently, eco-friendly modes of transport.

We also analyzed the relationship between socio-economic variables and the results of the Ecological Behavior Scale. Partially agreeing with Mónus [27] and Hypothesis 3, the scores were higher among female adolescents and public school students. This suggests that interventions should target males and students in private schools first and foremost.

Although the adolescents’ current journey to school is important, because of greenhouse gas emissions and habit formation right now, this study sheds light on the future, as we examined which variables influence the choice of more sustainable modes of transport over a 15-year period. Current habits did not significantly predict the choice of more sustainable modes of transport, rejecting H4a. The reason for this could be that at present, the adolescents have to obey their parents. As expected, two of the three TPB factors showed a significant influence: subjective norms (more specifically descriptive norms) and attitudes, which confirms H4b. Important people (significant social referents) using the same mode of transport as adolescents had a great influence on their choice of more sustainable mode of transport, corroborating previous studies [28,29]. Our findings highlight the important role played by parents in the adolescent’s pro-environmental behavior. Therefore, as Collado and colleagues [28] suggested, environmental education should be aimed at parents. Indeed, considering the positive impact of social support on adolescents’ choice of active transport [23], careful attention should be paid to the role of significant others when planning interventions.

Regarding attitudes, our study suggests that the more positive the attitude towards the chosen mode of transport for the future, the more polluting the chosen mode of transport was. This means that young people still have a very positive attitude towards car use and do not see many advantages in using eco-friendly modes such as bicycles. While the significant advantages of choosing more eco-friendly modes of transport were practicing physical exercise and protecting the environment, the disadvantages were the impossibility of carrying things or people, getting tired, and the risk of sexual harassment. This means that in addition to campaigns to improve attitudes toward walking, cycling, or using public transport, public safety needs to be improved. Thus, people would feel safe in public spaces without being in their private cars.

Regarding adolescents’ ecological behavior, our results showed that adolescents who were more committed to refusing to use products considered harmful to the environment (Activism-consumption) tended to choose a sustainable mode of transport for the future. However, the other factors on the Ecological Behavior Scale were not significant, suggesting that it is important to focus on education about the impact that the modes of transport have on the environment.

Environmental education needs to be taken seriously in Brazilian schools, not only to comply with the law [37], but also so that adolescents actually adopt more pro-environmental behavior, creating benefits for their community and themselves [26]. Since the present study showed that activism and subjective norms had a significant impact on the choice of sustainable modes of transport, we propose the following six steps to be implemented in schools. First, prepare teachers for the topic through partnerships with non-governmental organizations [25]. Second, teachers should discuss with students the importance of collective issues, and future orientation [30]. Third, teachers should present theoretical elements to students through texts and videos. At this stage, it is important for students to know the environmental impact of transportation and to understand how much CO₂ their daily commute would produce using each mode of transport. In this lesson, teachers could give clear information, for example, that it is more sustainable to use public transport than a car. Fourth, encourage the use of virtual reality and computer games to change climate attitudes and environmental self-efficacy [34]. Fifth, take adolescents out of school to collect data on air pollution [25]. At this stage, parents can be involved [28], considering the importance of descriptive norms. The results can be discussed together. Finally, offer incentives to students who engage in environmentally friendly behavior. For example, the school could offer a reward to those who use micro-mobility or public transportation to get to class.

This study presents some limitations linked to the lack of representativity of the various specificities in Brazil (e.g., urban versus rural cities, small cities, more regions of Brazil, etc.). Additionally, sample variables could be more balanced (e.g., gender, age, etc.). Due to the time needed to comply with the ethical procedures required to administer questionnaires to minors (permission from the school, parents, and adolescents), it was not possible to carry out the survey in more cities. Although the city was not a significant variable in any of the analyses, it would be interesting for future research to include all sizes of cities to make the sample more representative.

5. Conclusions

At the time we were finalizing this paper, the British government apologized for the death of Ella, a 9-year-old girl, who is believed to be the first person in the U.K. to have air pollution listed on her death certificate [47]. Ella, who grew up just 25 m (yards) from the South Circular Road, a major conduit for traffic along the southern edge of central London, was exposed to levels of nitrogen dioxide and particulate matter that exceeded World Health Organization guidelines, and the limits set by European Union and domestic law. A decade-long battle after Ella’s death highlighted the risks vehicle emissions pose to children in low-income communities and that the governments can be held to account for their failures in relation to air pollution.

Air pollution is clearly a public health issue and governments around the world have the responsibility for improving the air quality we breathe. Failing to protect the environment poses a serious threat to human health. As aforementioned, educating young people and their parents regarding the invisible risk of air pollution represents one of the measures to adopting pro-environmental behavior. Indeed, we found that subjective norms, attitudes, and active participation in environmental groups influence intended sustainable transport choices in 15 years’ time. Our results can be used to inform governments’ policy to support classroom education and other interventions aimed at protecting the environment. In summary, interventions need to provide information on the environmental impact of transport, but above all, they need to improve young people’s attitudes towards using environmentally friendly modes of transport. Involving parents in this discussion is an effective strategy, according to our findings and to the literature [28].