Influence of maternal past non-transport pro-environmental behaviours on young adults ’ sustainable transport

This UK-focused longitudinal study examines the influence of maternal past non-transport, pro-environmental actions (e.g. eco-friendly shopping and energy-saving behaviours during their children ’ s adolescence) on children ’ s sustainable transport behaviours as young adults. It also explores the role of children ’ s pro-environmental attitudes as young adults in this influence. Structural equation modelling was used to explore these complex interactions based on data from 977 mother – child pairs in waves 4 and 10 of the UK Household Longitudinal Study. Findings reveal that maternal past non-transport, pro-environmental behaviours positively influence children ’ s pro-environmental attitudes as young adults. While no direct influence of these maternal behaviours on children ’ s sustainable transport behaviours as young adults was found, an indirect influence was observed, mediated through children ’ s pro-environmental attitudes as young adults. This study not only provides a new perspective for understanding the origins of sustainable transport behaviours in young adults, but also reveals pathways of intergenerational transmission of pro-environmental behaviours.


Introduction
The transport sector remains a substantial contributor to global greenhouse gas emissions, posing considerable environmental challenges (Lamb et al., 2021).This is particularly pronounced in the UK, where transport sector emissions have exceeded those of the energy sector, comprising 26 % of the national total in 2019 (Department for Transport, 2021).Given that cars and taxis are responsible for over half of domestic transport emissions, the promotion of sustainable transport behaviour, such as walking, cycling and public transit, is essential for mitigation (AlKheder, 2021;Byrne et al., 2021).Young adults (18-25 years) are a pivotal demographic in this context (Arnett, 2000).Research indicates that sustainable transport behaviours formed during early adulthood often persist, having a lasting impact on sustainable transport choices throughout life (De Vos et al., 2022;Sigurdardottir et al., 2013).Therefore, it is necessary to explore the determinants of young adults' sustainable transport behaviours to inform interventions.
Previous research has identified various factors, including socioeconomic aspects such as employment status and income, demographic characteristics such as sex and ethnicity, early-life transport experiences and psychological constituents such as transport and pro-environmental attitudes, as key influencers of sustainable transport behaviours among young adults (Jamal and Newbold, 2020;Mjahed et al., 2015;Van Acker et al., 2019).Notably, Haustein et al. (2009) recommend broadening the scope of research on determinants of transport behaviours among young adults to include the socialization process they experience leading up to adulthood.Evans et al. (2018) found that when mothers exhibit pronounced pro-environmental attitudes and behaviours, including those related to sustainable transport, during their children's childhood socialisation, their children are more likely to emulate such behaviours into young adulthood.However, this study framed parental and their children's pro-environmental behaviours as a generalized concept, encompassing energy conservation, sustainable transport, green shopping, recycling, and social engagement.Lynn (2014) argued that sustainable transport behaviours face greater constraints (ranging from inadequate infrastructure and limited accessibility to sustainable modes of transport) compared to non-transport pro-environmental behaviours like energy conservation or green shopping.Therefore, it is essential to discuss them separately rather than as a generalized concept (Karlin et al., 2012).In terms of sustainable transport behaviours, Klöckner and Matthies (2012) found that parents' high frequency use of public transport before their children become young adults negatively influences their children's habitual car usage as young adults.Döring et al. (2019) further noted that children's negative attitudes towards car use in young adulthood can act as a mediator in this influence.
However, a considerable gap exists in understanding the influence of parental non-transport pro-environmental behaviours (e.g.green shopping and saving energy) and pro-environmental attitudes preceding the adulthood of their children on children's subsequent sustainable transport behaviours as young adults.It is suggested that these parental behaviours and pro-environmental attitudes may contribute to the early development of pro-environmental attitudes in their children as young adults (Collado et al., 2017;Leppänen et al., 2012).These attitudes could potentially solidify during emerging adulthood and manifest in various proenvironmental actions, including sustainable transport behaviours (Bouscasse et al., 2018;Hess et al., 2013).Thus, parental nontransport pro-environmental behaviours and pro-environmental attitudes preceding the adulthood of their children could indirectly influence children's sustainable transport behaviours as young adults through the mediation of children's pro-environmental attitudes as young adults.Despite this theoretical framework, empirical evidence demonstrating this mediating influence is currently lacking.
This UK-focused longitudinal study aims to explore these research gaps.Considering that mothers' pro-environmental behaviours exert a greater influence on their children's similar behaviours compared to those of fathers (Collado et al., 2019), and recognizing adolescence as a pivotal period for the development of lifelong behaviours and attitudes before entering young adulthood (Steinberg, 2001), this study focuses on mothers' behaviours and attitudes when their children are adolescents.Specifically, this study examines the indirect influences of maternal non-transport pro-environmental behaviours and pro-environmental attitudes when their children are adolescents (aged 12 to 15) on their children's sustainable transport behaviours subsequently as young adults (aged 18 to 25).The study also aims to explore the role of children's pro-environmental attitudes in young adulthood in shaping these influences.Based on research aims and previous research, this study mainly examines three hypotheses.
Hypothesis 1.The non-transport, pro-environmental behaviours and pro-environmental attitudes exhibited by mothers during their child's adolescence influence their child's pro-environmental attitudes in young adulthood.
Hypothesis 2. Mothers' non-transport, pro-environmental behaviours and pro-environmental attitudes during their child's adolescence indirectly influence their child's sustainable transport behaviour in young adulthood.
Hypothesis 3. The influence of the non-transport, pro-environmental behaviours and pro-environmental attitudes exhibited by mothers during their child's adolescence on their child's sustainable transport behaviours as young adults are mediated by the child's pro-environmental attitudes in young adulthood.
Fig. 1 illustrates the hypothesised pathway of influence that this study seeks to examine using structural equation modelling.This study introduces a new perspective for understanding the origins of sustainable transport behaviours in young adults.Moreover, this study has implications for understanding how pro-environmental behaviours are transmitted intergenerationally between parents and children.

Literature review
To refine the research questions and select control variables, section 2.1 conducts a literature review on determinants of transport behaviours among young adults.Section 2.2 discusses the potential influence of parents' non-transport pro-environmental behaviours and attitudes during their children's adolescence on their children's sustainable transport behaviours as young adults, along with the role of young adults' own pro-environmental attitudes in this influence.J. Li et al.

Determinants of transport behaviours among young adults
Transport choices among young adults are significantly influenced by demographics and socioeconomic factors.Research indicates that young men tend to favour walking or biking (Nash and Mitra, 2019), while young women are more inclined towards public transport (Newbold and Scott, 2018).Ethnic background also plays a crucial role, as evidenced in the UK where Black and Asian individuals typically accumulate fewer car miles than their white British peers, which is thought to stem from socioeconomic variations across ethnic groups (Mattioli and Scheiner, 2022).Socioeconomic aspects, particularly employment status and income, have a strong impact on transport decisions.Once young adults finish school and start working, they typically use cars more and public transport less (Busch-Geertsema and Lanzendorf, 2017).Students, often limited by their budget, tend to use public transport more often (Newbold and Scott, 2018).As young adults' incomes grow, they are more likely to drive and use cars for daily commuting (Blumenberg et al., 2012;Simons et al., 2017).Young middle-class people exhibit tendencies towards car-centric behaviour, while those from economically disadvantaged backgrounds are less inclined to opt for car transportation (Groth et al., 2021).
Life changes, particularly those linked to different life stages, impact the transport choices of young adults.When young adults move out of their parents' home, they typically reduce their reliance on public transport and are more likely to drive, carpool or get a driver's licence (Blumenberg et al., 2012;Le Vine and Polak, 2014).It is crucial to note that buying a car or securing a driver's licence heralds a profound life transition, often leading to increased car dependency within this age group (Vale et al., 2018).
Residential location and its surrounding infrastructure play an important role in influencing young adults' transport choices.When adolescents reside in urban areas where there is a substantial amalgamation of diverse land uses, effectively blending workplaces, educational institutions and leisure amenities, leading to reduced travel distances, their inclination towards adopting active and public transport patterns becomes more pronounced, consequently decreasing their dependence on cars (Simons et al., 2017).Conversely, living in rural areas necessitates more cars use due to greater travel distances (De Paepe et al., 2018;Licaj et al., 2012).Furthermore, characteristics of the built environment, which include factors such as road layout, proximity to essential services and the availability of safe cycling infrastructure, exert a substantial influence on the sustainable transport preferences of young adults (Habib et al., 2018;Simons et al., 2014).Nevertheless, Nash and Mitra (2019) present a more intricate perspective, proposing that the initial transport preferences of young adults could influence their decisions about where to live, subsequently shaping their transport behaviours.The authors present relevant examples to show that individuals with a preference for cycling might be drawn to neighbourhoods with welldeveloped cycling infrastructure, while those with a preference for cars could opt for areas more accommodating to car use.Moreover, studies on the relationship between the built environment and transport behaviours often incorporate individual and household-level socioeconomic factors, yet a paradox emerges as communities with similar socioeconomic conditions exhibit diverse transport patterns (Jamal and Newbold, 2020).This underscores the fact that although the influence of the built environment and socioeconomic factors at the individual and household levels play an important role in young adults' transport behaviours, the variations in transport behaviours imply that the presence of additional factors may influence transport behaviours.Anable (2005) highlights that beyond objective elements such as socioeconomic status or costs, young adults' psychological factors such as intrinsic beliefs, values and attitudes can considerably influence travel behaviour.For example, young adults' pro-environment attitudes increase the chance of using active transport (walking and cycling) and decrease driving (Davis et al., 2012;Nash and Mitra, 2019).Moreover, pro-car attitudes, including those that associate cars with notions of independence and safety, negatively impact sustainable transport behaviours among young adults (Busch-Geertsema and Lanzendorf, 2017;Lavieri et al., 2017;Nash and Mitra, 2019).Haustein et al. (2009) suggest expanding the research focus on factors influencing transport behaviours among young adults to encompass the experiences of socialization process they undergo as they transition into adulthood.For example, experiences with specific modes of transport have been identified as the potential roots of future travel behaviours (Van Acker et al., 2019).This is rooted in the idea that recurrent past behaviours can evolve into habits that influence future actions (Bamberg and Schmidt, 2003).If consistent car usage results in favourable outcomes such as comfort and efficiency in transport, this can lead to the development of habitual car usage (Verplanken et al., 2008).Similarly, Carrus et al. (2008) contend that historical behaviours, such as a consistent preference for public transport over private cars, serve as substantial indicators of the inclination to use public transport habitually in future.
In addition, young adults' psychological factors such as the attitudes toward transport mode are also influenced by past socialization experiences, offering a pathway to explore the origins of their transport behaviours.For instance, Döring et al. (2019) propose that parents who exhibit high rates of car usage or hold positive attitudes towards cars during their children's teenage years can positively influence their children's pro-car attitudes in adulthood, thereby impacting their children's car usage for commuting as adults.This suggests that parents' transport-related behaviours and attitudes during their children's adolescence can influence their children's attitudes towards modes of transport in adulthood, thus indirectly shaping children's transport behaviour in young adulthood.However, it remains to be explored whether there are similar influences of parents' non-transport behaviours, such as ecofriendly shopping and energy conservation, during their children's adolescence.Investigating these non-transport behaviours could reveal additional pathways through which parental influence shapes young adults' transport behaviours.This broadens the understanding of how pro-environmental behaviours are transmitted across generations and how parental pro-environmental behaviours influence their children's a range of behavioural outcomes, including those related to transport.

The role of parents' non-transport, pro-environmental behaviours and pro-environmental attitudes during their children's adolescence
Social learning theory emphasises the pivotal role that parents' behavioural patterns and attitudes play in shaping the behaviours of J. Li et al. their offspring (Bandura and McClelland, 1977).Prior studies have demonstrated that parents' pro-environmental attitudes and nontransport pro-environmnteal actions during their children's teenage years, such as eco-friendly shopping, waste reduction, and energy conservation, are positively correlated with similar behaviours observed in their children during the same period (Collado et al., 2017;Grønhøj andThøgersen, 2009, 2012).It is noteworthy that this correlation seems to be mediated by the psychological construction of children as adolescents.For example, Wallis and Klöckner (2018) found that among teenagers, the perception of their parents' behaviours served as a mediator when both parties engaged in the same energy-saving actions.Similar conclusions were drawn by Jia and Yu (2021) while analysing parental and teenage behaviours in energy-saving and waste reduction and disposal.Moreover, Gong et al. (2022) posited that parents' green consumer habits directly shape the value systems of teenagers, which, in turn, greatly foster the formation of their eco-friendly consumption habits.In addition, Collado et al. (2017) found that not only parents' waste management practices and resource conservation behaviours but also their pro-environmental attitudes can considerably influence the proenvironmental attitudes of adolescent offspring and determine children's behaviours.Early research has found the correlation between fathers' pro-environmental attitudes and similar attitudes in their children (Guastello and Peissig, 1998;Leppänen et al., 2012).These findings suggest that parents' non-transport, pro-environmental behaviours and pro-environmental attitudes can shape similar behaviours of their children as adolescents by impacting children's psychological factors related to environmentalism.This viewpoint is endorsed by Grønhøj and Thøgersen (2017), who argue that the adoption of sustainable practices by young people is not a mere imitation of parental behaviours, rather, through continuous observation of parental actions, offspring develop an intrinsic motivation to engage in pro-environmental activities.This motivation signifies that observed behaviours become fully integrated into the individual's identity, aligning with their own attitudes and values (Deci and Ryan, 1985).
However, a question is whether the relationship between parental non-transport pro-environmental behaviours and proenvironmental attitudes and their children's psychological factors (such as pro-environmental attitudes) during children's adolescence persists into children's young adulthood.In other words, it is still ambiguous if there is a correlation of parents' non-transport pro-environmental behaviours and pro-environmental attitudes during their children's teenage years with children's proenvironmental attitudes in young adulthood.However, drawing from research on other attitudes, the attitudes formed towards social and political issues during adolescence tend to endure throughout an individual's life (Alwin and Krosnick, 1991;Sears and Funk, 1999).A longitudinal study also indicates that parental pro-car attitudes during children's adolescence influences children's pro-car attitudes and negative attitudes toward walking as adults (Mjahed et al., 2015).It can be hypothesised that parents' non-transport, proenvironmental behaviours and attitudes during their children's adolescence have the potential to influence their children's proenvironmental attitudes in adulthood.Given that pro-environmental attitudes in early adulthood are seen as determinants of sustainable transport behaviours (Bouscasse et al., 2018), children's pro-environmental attitudes in early adulthood may mediate the relationship of parents' non-transport, pro-environmental behaviours and pro-environmental attitudes during their children's adolescence with children's sustainable transport behaviours in young adulthood.However, no study has yet examined this issue.
This longitudinal study was conducted to explore the above-mentioned research gaps.It is worth noting that mothers exert a greater influence than fathers in shaping the education, behaviours and attitudes of their children (Matthies et al., 2012).In terms of intergenerational transmission of pro-environmental behaviours, Collado et al. (2019) have highlighted that when both mothers and fathers engage in the same environmentally friendly behaviours, the observed environmentally friendly behaviours of mothers have stronger strength of influence on their children's similar pro-environmental behaviours compared to the observed behaviours of fathers.These findings collectively emphasize the crucial role mothers play in influencing their children's behaviour and development.As a result, this study focuses primarily on the examination of mothers' attitudes and behaviours.

Samples
This study adopted a longitudinal research approach, using data from the UK Household Longitudinal Study (UKHLS), also known as the Understanding Society survey (University of Essex, 2019).The UKHLS is a longitudinal database that chronicles responses from a consistent, representative cohort of individuals over several years.It is an annual survey that provides detailed information on demographic, socioeconomic and household characteristics in the UK.Regarding the representativeness of the UKHLS, Davis-Kean et al. (2017) indicated that UKHLS closely mirrors the UK population.In addition, Fisher (2020) highlighted the similarity between the UKHLS and the UK Family Resources Survey concerning maternal attributes such as age, household size, ethnicity and region.This implies that the UKHLS represents this demographic effectively within the UK population.
An important aspect of the UKHLS is the assignment of a unique personal identifier to each participant to ensure that the respondents is accurately tracked across different waves of the survey.The UKHLS is organised around three main questionnaires.First, the household survey (a) focuses on household structure and socioeconomic aspects, including factors such as location (urban and rural) and income.Second, the Individual Survey (b) collects detailed information on the socio-demographic attributes, behaviours and attitudes of all individuals aged 16 years and older in the selected households, covering factors such as sex, ethnicity, employment status and pro-environmental attitudes and behaviours.Finally, the Youth Survey (c) seeks to understand the behavioural patterns and attitudes of 10-15-year-old adolescents, with a particular focus on their preferences for commuting to and from school.To ensure the precise identification of mothers within the adolescent respondents, the Youth Survey (c) incorporates unique maternal identifiers that can be mapped to personal identifiers in the Individual Survey (b).
This study used data from Waves 4 (2012/13) and 10 (2018/19) of the UKHLS.In Wave 4, 47,071 individuals aged 16 and older completed the Individual Survey (b) and 4,045 adolescents aged 10-15 completed the Youth Survey (c).Wave 10 involved 33,318 respondents aged 16 and above who completed the Individual Survey (b).The selection of these waves was based on the inclusion of essential variables in this study such as pro-environmental behaviours, attitudes and sustainable transport behaviours.In addition, the 6-year interval between waves allowed for capturing the transition of adolescents aged 12-15 into young adults aged 18 or above.
The primary objective of this study was to analyse the influence of the pro-environmental attitudes and non-transport, pro-environmental behaviours exhibited by mothers during their children's adolescence on the sustainable transport behaviours those children enact on transitioning into early adulthood.This objective can be achieved by correlating mothers' pro-environmental attitudes and behaviours from their children's adolescent phase (captured in Wave 4) with the sustainable transport behaviours adopted by children in their young adulthood (captured in Wave 10).In operationalising this, young people from Wave 4′s Youth Survey (c) were paired with their corresponding information as young adults in the Individual Survey (c) of Wave 10, facilitated by their distinct personal identifiers.Concurrently, the maternal identifier from Wave 4′s Youth Survey (c) provided a conduit to associate these adolescents with their respective mothers in the same wave's Individual Survey (b).This approach culminated in a unified dataset that comprehensively reflects information about mothers when their children are adolescents and information about their children in adulthood.After merging the datasets, respondents of 1,306 mother-child dyads were initially identified.However, by discarding those pairs with incomplete data and filtering to include only children aged 18 or older, the respondents were narrowed down to 977 mother-young adult pairs.

Variables
In this study, the primary variables examined were the pro-environmental attitudes and sustainable travel behaviours of children in young adulthood and the pro-environmental attitudes and non-transport behaviours of their mothers during their child's adolescence.To gauge the sustainable transport behaviours of children in young adulthood, this study employed two specific survey items in Wave 10 of the UKHLS.The first pertained to the frequency with which participants chose to walk or cycle (active transport) for shorter journeys, specifically those covering a distance of 2 to 3 miles.The second enquired about their frequency of using public transport, such as buses or trains, as an alternative to driving.Participants responded on a scale ranging from 1 (never) to 5 (always).The selection of these survey items is rooted in their ability to capture the frequency of adopting active and public modes of transport over car travel, serving as a reliable proxy for sustainable transport behaviours.Moreover, by incorporating travel distance restrictions in the questions related to active transport, the study aptly controlled for the potential influence of distance on transport mode choice.In addition, this study also considered mothers' sustainable transport behaviours during their children's adolescence, and the survey items chosen were consistent with the sustainable transport behaviours of children in young adulthood.It is worth noting that survey items for mothers' sustainable transport behaviours during their children's adolescence were derived from Wave 4 of the UKHLS.Table 1 shows the mean values for each of these two survey items for mothers and children, where higher averages indicate more prevalent behaviours.

Survey items Mean (SD)
Children's pro-environmental attitudes in young adulthood (1.Strongly Agree ~ 5. Strongly Disagree) (Wave 10) Any changes I make to help the environment must fit with my lifestyle 2.85 (0.88)The so-called 'environmental crisis' has been greatly exaggerated 3.54 (1.04) Climate change is beyond our control; it is too late to do anything 3.51 (0.95) The effects of climate change will occur too far in the future to truly worry me 3.66 (1.07)It is not worthwhile for me to do things to help the environment if others do not.2.82 (0.88)The so-called 'environmental crisis' has been greatly exaggerated.
3.09 (0.89) Climate change is beyond our control; it is too late to do anything.
3.42 (0.89)The effects of climate change will occur too far in the future to truly worry me.
3.52 (0.91)It is not worthwhile for me to do things to help the environment if others do not.
3.42 (1.03)It is not worthwhile for the UK to combat climate change because other countries will cancel out what it does.
To understand the non-transport, pro-environmental behaviours of mothers during their child's adolescence, emphasis was placed on everyday family activities with environmental relevance that mothers often participate in.McKenzie-Mohr et al. (1995) highlighted the importance of encompassing activities with diverse motivations, opportunities and participation capabilities.This approach mitigates the risk of yielding results restricted to the parameters of specific behaviours.In addition, the observability of the mothers' behaviours towards the offspring is critical.Matthies et al. (2012) found that intergenerational transmission of pro-environmental behaviours was only possible if the children observed their mother's pro-environmental behaviours.Consequently, maternal green shopping and energy conservation behaviours were chosen, as shown by Grønhøj and Thøgersen (2017) to influence similar tendencies in offspring.This study comprises six survey items such as 'Do not keep the tap running while you brush your teeth' (see to Table 1) in Wave 4, to gauge maternal engagement in non-transport, pro-environmental behaviours.The engagement level is rated on a scale from 1, indicating 'never', to 5, indicating 'always'.From Table 1, it is evident that the behaviour of switching off lights in unoccupied rooms was prevalent (mean = 4.41), yet mothers appeared less inclined to avoid products with excessive packaging (mean = 1.81).This disparity underscores the comprehensive nature of the survey items employed to assess mothers' non-transport pro-environmental behaviours (McKenzie-Mohr et al., 1995).
Concerning the children's pro-environmental attitudes in young adulthood and the mothers' pro-environmental attitudes during children's adolescence, the study incorporated the same six items for each group.For example, a survey item is, 'The "environmental crisis" facing humanity is considerably exaggerated'.Respondents rated their agreement on a 5-point Likert scale, with 1 representing 'Strongly Agree' and 5 denoting 'Strongly Disagree'.In this framework, a higher score signifies intensified pro-environmental convictions or heightened endorsement of environmental preservation.The other five survey items are listed in Table 1, all of which fall under the same heading as the example above.These survey items are anchored in the New Ecological Paradigm Scale (Dunlap et al., 2000).This scale, stemming from in-depth environmental research that began in the 1970 s, has been systematically refined throughout the years.Data concerning children's pro-environmental attitudes as young adults were sourced from Wave 10 of the UKHLS, while the corresponding data for mothers, recorded during the children's adolescence, were drawn from Wave 4 of the UKHLS.
Drawing on the existing literature, this study incorporates a wide range of control variables.These variables encompass young adults' demographic attributes such as age, sex and ethnicity.In addition, income levels and geographical settings (urban versus rural) are also considered.The study further explores young adults' socioeconomic attributes by considering factors such as their current employment situation.Moreover, young adults' life change, such as whether they own a car, have a driving licence and live with their parents, are considered in this study.Notably, the study also reflects the past transport behaviour of young adults during their adolescent years, focusing on their transport choice to school.Table 2 provides details on the control variables of respondents.In the Appendix, Table A.1 compares the respondents from this study with all young adult respondents aged 18-21 as captured in Wave 10 of the UKHLS.There are no statistically significant differences found in the variables' distribution across both the study's respondents and all young adults captured in Wave 10 of the UKHLS.This suggests that to some extent our study's respondents is as representative of the UK population as the full UKHLS respondents.

Structural equation modelling
The study uses SEM to uncover intricate connections between mothers' pro-environmental attitudes and non-transport behaviours during their children's youth and their children's pro-environmental attitudes and sustainable transport behaviour in their adult years.SEM traditionally has two main components: a measurement model and a structural model.The former elucidates how visible variables define the latent ones, and the latter depicts the relationship between the latent factors.Structural equation modelling (SEM) offers more than just insights into direct relationships between variables; it is adept at unveiling indirect associations via mediating variables (Kaplan, 2008).Thus, the overall effect encapsulates both direct and mediated influences.This approach aligns seamlessly with the aim of this study: to investigate the mediating role of pro-environmental attitudes of children during early adulthood in the relationship between their mothers' pro-environmental attitudes and non-transport behaviours during the children's adolescence and the sustainable transport choices these children make in their young adult lives.
Using SEM techniques and considering the available data and factors, a model was constructed to elucidate the complex relationships under investigation in this study.As illustrated in Fig. 2, in the measurement model, mothers' pro-environmental attitudes and behaviours during their children's adolescence and their children's pro-environmental attitudes and sustainable transport behaviours in early adulthood, serve as latent variables.These latent variables are derived from the observable survey items associated with each.In the structural model, exogenous variables encompass young adults' current demographic and socioeconomic attributes (such as age, gender, race, employment status and highest educational level achieved), life choices (including car ownership, possession of a driver's licence and living with mothers), past transport behaviour (transport choice to school during adolescence), household attributes (household income and residential location) and mothers' pro-environmental attitudes during their children's adolescent years.Conversely, the child's pro-environmental attitudes and sustainable transport behaviours in early adulthood are treated as endogenous variables.It should be noted that because mothers' non-transport, pro-environmental behaviours and sustainable transport behaviours during their children's adolescence are shaped by their pro-environmental attitudes (Flamm, 2009; Fig. 2. Conceptual framework illustrating the anticipated associations within the SEM. J. Li et al. Hidalgo-Crespo et al., 2022), such behaviours also qualify as endogenous variables.Within Fig. 2, ovals denote latent variables, and rectangles denote measured variables.Variables in purple symbolise the endogenous factors, and those in yellow represent exogenous factors.
Based on self-perception theory, previous research suggests that sustainable transport actions may inversely affect people's proenvironmental attitudes (Bem, 1972).However, this study failed to identify any notable inverse effect on evaluating the two-way relationship between young adults' pro-environmental attitudes and their sustainable transport behaviours.Therefore, only oneway connections were considered in the finalised model.The model was implemented within the Mplus framework, employing the WLSMV (Weighted Least Squares Mean and Variance Adjusted) estimator, given the non-normal distribution of the dependent ordered categorical variables.To assess the appropriateness of the structural equation model, various fit indices were employed.Typically, Mplus provides metrics such as the chi-square (χ2) statistic, the root mean square error of approximation (RMSEA), the Tucker-Lewis index (TLI), the comparative fit index (CFI) and the standardised root mean square residual (SRMR).

Results and discussion
Table 3 presents the goodness-of-fit indices, suggesting that the model is generally well-fitted to the data, while the chi-square test is substantial at the 0.05 level, which typically indicates a misfit.However, the chi-square statistic is nonparametric and is impacted by respondents' size (Schermelleh-Engel et al., 2003).In the case of large respondents, even a minor deviation from a perfect fit can yield statistically substantial chi-square test results (Alavi et al., 2020).Therefore, chi-square does not contribute to the understanding of the fit of models with large respondents' sizes (such as the present model), but it is reported for completeness.
We calculated the TLI, CFI and RMSEA.Both the TLI and CFI exceed the often-recommended threshold of 0.90, indicating a good fit.Furthermore, the RMSEA is below the preferred level of 0.05 and the SRMR is below the benchmark of 0.08; thus, the model's robustness is further corroborated (Mueller and Hancock, 2001).In the same table, the standardised parameter estimates for the 22 survey items relating to attitudes and behaviours are provided.Each survey item aligns well with its associated latent factor, as evidenced by the factor loadings.Notably, these loadings are predominantly of a satisfactory magnitude, exceeding the commonly accepted threshold of 0.3 (Kang and Ahn, 2021).
Table 4 illustrates the standardised direct and indirect effects of a mother's pro-environmental attitudes and behaviours during her child's adolescence, on the child's pro-environmental attitudes in adulthood.Regarding a mother's non-transport, pro-environmental behaviours and sustainable transport behaviours during her child's adolescence, it was evident that the mother's pro-environmental

Table 3
Factor analysis estimates and model fit indices (N = 977).

Survey items
Standardised parameter estimate P-Value

Children's pro-environmental attitudes in young adulthood
Any changes I make to help the environment must fit with my lifestyle.0.380 0.000 The so-called 'environmental crisis' has been greatly exaggerated.
0.715 0.000 Climate change is beyond our control; it is too late to do anything.0.617 0.000 The effects of climate change will occur too far in the future to truly worry me.0.771 0.000 It is not worthwhile for me to do things to help the environment if others do not.0.660 0.000 It is not worthwhile for the UK to combat climate change because other countries will cancel out what it does.0.816 0.000 Children's sustainable transport behaviours in young adulthood Opting for public modes of transport, such as buses or trains, over car travel.0.761 0.000 Walking or cycling for short journeys of less than 2 or 3 miles.0.610 0.000 Mother's non-transport pro-environmental behaviours during their children's adolescence Not leaving the tap running while you brush your teeth.0.336 0.000 Turning off lights in rooms not in use.
0.306 0.000Not leaving the TV on standby for the night.0.354 0.000Not buying something because of too much packaging.0.528 0.000 Buying recycled paper products.0.626 0.000 Taking along a shopping bag for shopping.0.391 0.000 Mothers' sustainable transport behaviours during their children's adolescence Opting for public modes of transport, such as buses or trains, over car travel.0.722 0.000 Walking or cycling for short journeys of less than 2 or 3 miles.0.543 0.000 Mother's pro-environmental attitudes during their children's adolescence Any changes I make to help the environment must fit with my lifestyle.0.368 0.000 The so-called 'environmental crisis' has been greatly exaggerated.
0.520 0.000 Climate change is beyond our control; it is too late to do anything.0.565 0.000 The effects of climate change will occur too far in the future to truly worry me.0.697 0.000 It is not worthwhile for me to do things to help the environment if others do not.
0 attitudes at the time considerably positively influenced both.Given that standardised coefficients can indicate the strength of these influences, the data suggest that a mother's pro-environmental attitudes have a stronger direct influence on her non-transport, proenvironmental behaviour than on her sustainable transport behaviour (β = 0.380 compared with 0.166).The results mirror the insights presented by Lynn (2014), which emphasised the greater constraints (ranging from inadequate infrastructure and limited accessibility to sustainable modes of transport) that individuals face when navigating sustainable transport decisions compared with other ecofriendly choices such as energy conservation or green shopping.Given these intricate constraints, the weight of pro-environmental attitudes in guiding sustainable transport choices is diluted (Biggar and Ardoin, 2017).In contrast, decisions in areas with fewer external constraints, such as household energy use or eco-friendly purchasing, might be more directly aligned with one's proenvironmental attitudes.For children's pro-environmental attitudes in young adulthood, the mother's pro-environmental attitudes and her non-transport, pro-environmental behaviours during their child's adolescence have a direct influence (β = 0.154 and 0.226, p < 0.001).Moreover, the mother's pro-environmental attitudes during her child's teenage years can also influence her child's future pro-environmental attitudes indirectly via her non-transport, pro-environmental behaviours during that phase (β = 0.099, p < 0.001).These results support Hypothesis 1.The direct influence of a mother's non-transport, pro-environmental behaviours may be due to the observation and internalisation of these behaviours by their children during adolescence, which subsequently facilitates the development of proenvironmental attitudes (Collado et al., 2017).Regarding the direct influence of mothers' pro-environmental attitudes, engaging in discussions about the environment plays a pivotal role.Jia and Yu (2021) provided evidence that communications about environmental conservation between parents and their adolescent offspring serve as an essential catalyst in the propagation of proenvironmental behaviours across generations.From this, we could hypothesise that mothers' pro-environmental attitudes are, to a large extent, also transmitted to their children through parent-child communication.
Our data underscore that the mothers' non-transport, pro-environmental behaviours during their children's adolescence could demonstrate a stronger direct influence on their children's pro-environmental attitudes in adulthood, compared with the mothers' proenvironmental attitudes observed within the same period (β = 0.226 compared with 0.154).This finding could extend the findings of Grønhøj and Thøgersen (2012), suggesting that a mother's behaviours, rather than attitudes, have a more substantial influence on shaping not only their children's pro-environmental actions but also their pro-environmental attitudes in adulthood.This highlights the pivotal role of maternal behaviours in instilling lasting pro-environmental attitudes and practices in subsequent generations.
Moreover, the results suggest that mothers' sustainable transport behaviours during their children's adolescence do not have a direct effect on their children's pro-environmental attitudes in adulthood.A plausible explanation for this observation may be that due to the multiple constraints surrounding sustainable transport such as inadequate infrastructure may inadvertently obscure the proenvironmental motivations behind these decisions (Lynn, 2014).As a result, children may fail to recognize and internalize the proenvironmental concepts behind their mothers' sustainable transport choices so that they do not influence their pro-environmental attitudes as adults.This emphasises the need to enhance children's understanding of the motivations behind their parents' proenvironmental behaviours (Jia and Yu, 2021).Previous research has suggested that meaningful conversations between parents and their children about the contribution of sustainable transport to environmental protection can be instrumental in aiding children to truly understand and appreciate the motivation behind parental sustainable transport behaviours, thus, leading to children's sustainable behaviours (Haustein et al., 2009).
Table 5 presents the standardised coefficients of the direct and indirect influence of various socioeconomic, demographic and proenvironmental indicators on young adults' sustainable transport behaviours in the SEM model.Regarding socioeconomic traits, young adults from non-white ethnicities, compared with their white counterparts, displayed a heightened propensity towards sustainable transport behaviours (β = 0.085, p < 0.05).This validates the findings of a previous study conducted in the UK (Mattioli and Scheiner, 2022).Moreover, those who were employed (with full-time students as the reference group) exhibited a diminished sustainable transport inclination (β = − 0.179, p < 0.001).This could be attributed to the personal economic limitations students face regarding car travel, making them more inclined to opt for sustainable transport methods (Newbold and Scott, 2018).In addition, level of education is positively correlated with sustainable transport behaviours among young adults (β = 0.106, p < 0.001).This may be because young adults with higher educational qualifications tend to exhibit more favourable attitudes towards sustainable transport and have a rather negative stance on car use (De Vos and Alemi, 2020).
As expected, having a driver's licence and unrestricted access to a car adversely impacts young adults' inclination towards   sustainable transport.These observations align with previous research findings (Vale et al., 2018).Sustainable transport to school during young adults' adolescence (with car as the reference group) revealed a positive association with sustainable transport practices in young adulthood (β = 0.181, p < 0.001).Essentially, persistent engagement in sustainable transport to school during adolescence tends to solidify into entrenched sustainable transport habits, emerging as the default transport choice during young adulthood (Van Acker et al., 2019).Young adults' pro-environmental attitudes serve as a vital contributing factor to sustainable transport behaviours (β = 0.097, p < 0.05), indicating that intrinsic psychological constructions related to environmental protection considerably guide transport behaviours (Busch-Geertsema and Lanzendorf, 2017;Nash and Mitra, 2019).Moreover, maternal sustainable transport behaviours during children's adolescence impact children's sustainable transport behaviour as young adults (β = 0.303, p < 0.001).This finding is consistent with those of previous studies (Klöckner and Matthies, 2012).Importantly, the direct effects of mothers' pro-environmental attitudes and non-transport, pro-environmental behaviours during their child's adolescent years on the child's sustainable transport behaviours in young adulthood were not statistically substantial.However, when factoring in the young adults' pro-environmental attitudes, a substantial total indirect effect was observed (β = 0.091 and 0.022).This supports Hypothesis 2. Considering the seven potential mediation paths identified in the research model, a detailed exploration of these mediating influences is undertaken.
Table 6 reveals the path of indirect influence of mothers' pro-environmental attitudes and behaviours during their child's adolescence on the sustainable transport behaviours of that child as a young adult.First, mothers' pro-environmental attitudes during their child's adolescence play a pivotal role.When these attitudes influence her sustainable transport behaviours, there is an indirect effect on her child's sustainable transport behaviours in young adulthood (β = 0.05, p < 0.001).
In addition, another statistically substantial pathway emerges from the mother's pro-environmental attitudes during her child's adolescence, proceeding through her child's pro-environmental attitudes in young adulthood and culminating in her child's sustainable transport behaviours in young adulthood (β = 0.015, p < 0.05).The mother's non-transport, pro-environmental behaviours during her child's adolescence exert an influence on the child's pro-environmental attitudes in young adulthood.This, in turn, shapes the child's sustainable transport behaviours in their young adulthood (β = 0.022, p < 0.05).The findings thus validate Hypothesis 3, suggesting that a mother's pro-environmental attitudes and non-transport pro-environmental actions during her child's adolescence could indirectly shape her child's sustainable transport behaviours in young adulthood by moulding the child's pro-environmental attitudes in adulthood.The results could highlight the broader influence of mothers' pro-environmental attitudes and behaviours, which suggests that mothers' pro-environmental attitudes or any form of pro-environmental behaviour, even if not directly related to transport, can indirectly shape sustainable transport actions in the next generation.This provides a more comprehensive understanding of how parental attitudes and behaviours shape those of their children.
Moreover, previous studies have highlighted the significance of comprehensively evaluating measures aimed at fostering environmentally friendly behaviours (Steg and Vlek, 2009).The result of this study suggests that when assessing the effectiveness of interventions designed to encourage pro-environmental behaviours among target group, it is necessary to consider the long-term change in the diverse behaviours of the target group's children to a certain extent.For instance, in evaluating the influence of an intervention on maternal energy-saving or green shopping behaviours, the assessment should extend to include potential long-term shifts in their children's sustainable transport behaviours, alongside the immediate changes observed in maternal energy-saving or green shopping practices.
This study has two main limitations.First, it focuses on children's overall frequency of sustainable transportation behaviours in young adulthood across all travel purposes.However, different travel purposes face distinct constraints; for example, work-related travel often involves time constraints, leading to a preference for the most convenient modes, such as cars.Future studies should explore whether parents' non-transport environmental behaviours during children's adolescence still influence their adult children's work commuting choices.Second, this study focused only on the role of maternal behaviour.Future research should explore the potential impact of fathers and other family members on young adults' sustainable transport behaviours.

Conclusions
Using Waves 4 and 10 of the UKHLS survey, we presented a longitudinal exploration into the influence of mothers' proenvironmental attitudes and non-transport, pro-environmental behaviours during their children's adolescence on these children's pro-environmental attitudes and sustainable transport behaviours in young adulthood.The findings suggest that while there is no explicit direct link between these maternal attitudes and behaviours and their child's sustainable transport behaviours in adulthood, there exists an indirect effect that is entirely mediated through the pro-environmental attitudes of the child in adulthood.
Another contribution of the research is that, compared with a mother's pro-environmental attitudes during her child's adolescence, her behaviours during that period have a more substantial influence on her child's pro-environmental attitudes in adulthood.This confirms previous results on the influence of parents on their children's pro-environmental behaviours i.e., that behaviours consistently exhibit a stronger impact than attitudes (Grønhøj and Thøgersen, 2012).Importantly, our research extends this understanding, highlighting that the same principle applies when examining parental influences on the pro-environmental attitudes of their offspring in their adult years.
While the findings do not have direct policy implications, they do highlight a previously unexplored dimension of how parents' attitudes and behaviours might affect their children's sustainable transport behaviours.They also suggest that any policies or interventions which influence the pro-environmental behaviours of mothers can also indirectly influence the sustainable transport behaviours of their children in the future.These long-term impacts could be incorporated into the appraisal and evaluation of interventions.
3.34 (1.05)It is not worthwhile for the UK to combat climate change because other countries will cancel out what it does 3.63 (1.07) Children's sustainable transport behaviours in young adulthood (1.Never ~ 5. Always) (Wave 10) Opting for public modes of transport, such as buses or trains, over car travel 2.83 (1.43) Walk or cycle for short journeys of less than 2 or 3 miles 2.99 (1.42) Mothers' non-transport, pro-environmental behaviours during their children's adolescence (1.Never ~ 5. Always) (Wave 4) Not leaving the tap running while you brush your teeth 3.48 (1.63) Turning off lights in rooms not in use 4.41 (0.90)Not leaving the TV on standby for the night 3Opting for public modes of transport, such as buses or trains, over car travel.1.92 (1.21) Walking or cycling for short journeys of less than 2 or 3 miles.2.83 (1.38) Mothers' pro-environmental attitudes during their children's adolescence (1.Strongly Agree ~ 5. Strongly Disagree) (Wave 4) Any changes I make to help the environment must fit with my lifestyle.
− Mothers' pro-environmental attitudes during their children's adolescence → Mothers' non-transport, pro-environmental behaviours during their children's adolescence → Children's sustainable transport behaviours in young adulthood Specific indirect 2 0.05*** − Mothers' pro-environmental attitudes during their children's adolescence → Mothers' sustainable transport behaviours during their children's adolescence → Children's sustainable transport behaviours in young adulthood Specific indirect 3 0.015* − Mothers' pro-environmental attitudes during their children's adolescence → Children's pro-environmental attitudes in young adulthood → Children's sustainable transport behaviours in young adulthood Specific indirect 4 0.008* − Mothers' pro-environmental attitudes during their children's adolescence → Mothers' non-transport, pro-environmental behaviours during their children's adolescence → Children's pro-environmental attitudes in young adulthood → Children's sustainable transport behaviours in young adulthood Specific indirect 5 0.001 − Mothers' pro-environmental attitudes during their children's adolescence → Mothers' sustainable transport behaviours during their children's adolescence → Children's pro-environmental attitudes in young adulthood → Children's sustainable transport behaviours in young adulthood Indirect influence of mothers' non-transport pro-environmental behaviours Specific indirect 0.022* − Mothers' non-transport pro-environmental behaviours during their children's adolescence → Children's pro-environmental attitudes in young adulthood → Children's sustainable transport behaviours in young adulthood Indirect influence of mothers' sustainable transport behaviours Specific indirect 0.008 − Mothers' sustainable transport behaviours during their children's adolescence → Children's pro-environmental attitudes in young adulthood → Children's sustainable transport behaviours in young adulthood * Indicates significance at 0.05 level.** Indicates significance at 0.01 level.*** Indicates significance at 0.001 level.
adolescence: Sustainable transport to school = '1′, Going to school by car = '0′ 771 (78.9 %)Household factors (Wave 10)IncomeMonthly household net income, denoted as post-tax and national insurance deductions (in thousands of GBP), is adjusted for household size and composition using an equivalence scale.This equivalised income is calculated by dividing the net income by the provided equivalisation factor.
.792 0.000 It is not worthwhile for the UK to combat climate change because other countries will cancel out what it does.

Table 4
Standardised coefficients for direct and total indirect influences on latent variables.

Table 5
Standardised coefficients of the direct influence on children's sustainable transport behaviours in young adulthood.

Table 6
Standardised coefficients of the path of specific indirect effects on young adults' sustainable transport behaviours.

Table A .
1 (continued ) Income Monthly household net income, denoted post-tax and national insurance deductions (in thousands of GBP), is adjusted for household size and composition using an equivalence scale.This equivalised income is calculated by dividing the net income by the provided equivalisation factor.