Understanding Acceptability towards Sustainable Transportation Behavior, A Case Study of China

: Nowadays, increased usage of motorized vehicles has become a cause of serious environmental and health problems which results in noise pollution, air pollution and the emission of greenhouse gases. Sustainable transportation options such as green public buses, subways and public cycling have been introduced to improve environmental quality. However, their adoption is still in the initial stage. Therefore, the aim of this study is to explore the consumer attitude towards sustainable transportation, and their willingness to choose different environmentally friendly options like cycling and public green transportation by applying a norm activation model (NAM). More speciﬁcally, this study explored the role of different predictors (sustainable transport beneﬁts awareness, trafﬁc problem awareness, government policies and symbolic motives of using a car) affecting citizen’s acceptability to sustainable transportation options with mediating role of environmental concern and moderating role of self-transcendence and self-enhancement. A questionnaire-based survey conducted in four major metropolitan cities of China including Beijing, Shanghai, Guangzhou, and Xi’an found that acceptability towards sustainable transportation is derived from sustainable transport beneﬁts awareness and trafﬁc. Symbolic motives of the car have a negative association with acceptability towards sustainable transportation. The mediating effect of environmental concerns was proved, which extends the role of NAM in this study. Self-transcendence and self-enhancement have positive and negative moderating effects consecutively towards the acceptability of sustainable transportation. This study has potential implications for the government of China, transportation, and urban planning departments in order to take necessary measures to promote sustainable transportation behavior in Chinese citizens.


Introduction
The majority of the population of China consider the car as a convenient and attractive mode of transportation and heavily depend on a motorized vehicle in their daily life [1]. Nowadays, increased usage of the motorized vehicle has become a cause of serious environmental and health problems which are related to noise pollution, air pollution and the emission of greenhouse gas [2]. More dependence on motorized vehicles also disturbs our physical and mental health and can be a risk factor for chronic diseases [3]. The cost of different motorized vehicles is not a big issue and can be

Theoretical Framework
Schwartz [20] established the Norm activation model (NAM) by investigating the effect of norms on altruism and widely used in different kinds of pro-environment behavior. There are three types of antecedence that lead to pro-environment behavior. It includes awareness of consequences, the realization of responsibility and personal norms and values. The theory of NAM starts with an individual's understanding about the consequences and realization of responsibility for not performing the environmentally friendly behavior. Awareness of environmental issues triggers personal norms to avert harmful effects [21]. In this model, an individual's awareness is concerned with the common understanding of harmful effects for others; realization of responsibility is related to "ascription of responsibility" for adverse outcomes of not performing pro-socially or pro-environmentally; and personal norms and values are related to moral obligations that an individual possesses to perform social and environmentally friendly behavior. Moreover, an individual's understanding of consequences and realization of responsibility activates the personal norm system. It is due to assigning these negative consequences to themselves and take appropriate actions. Vice versa, if the feelings of negative consequences are not ascribed, the likelihood of ascribing responsibility is not developed. There are two schools of thought about using NAM in a model. Some researchers argue that NAM is a mediation-based model which describes that awareness and ascription of responsibility have an indirect effect on environmentally friendly behavior via personal norm [22][23][24][25]. Other researchers have assumed NAM to be a moderation-based model, as awareness of environmental issues and realization of responsibility moderates the association between personal norms and environmentally friendly behavior [26]. In this study, NAM is extended towards the adoption of sustainable transportation options by introducing a mediation-based model. With more awareness regarding transportation problems and the benefits of sustainable transportation, consumers will be more concerned about the environment. As environmental concern relates to a positive attitude towards environmental issues [27]; therefore, this study checks the validity of NAM in the current study based on ascribing responsibility to sustainable transportation and environmentally friendly practices.

Predictors of Acceptability to Sustainable Transportation
Since 2002, an adaptation of car usage has rapidly increased among Chinese citizens. China is standing as the number one car user with 24.4 million cars produced in the world [28,29]. In the literature, the alternatives to car-based transportation have gotten recognition as they decrease carbon in the transportation sector and because they provide improved public transport, give importance to those factors which can increase acceptability of alternatives and provisions of subsidies on renewable fuels [30]. The innovative new technologies including hybrids and electric vehicles, fuel cell vehicles (FCV), hydrogen, and electricity-and biofuel-based vehicles have replaced fuel-based personal transportation. Offer et al. [31] explored citizen's acceptability to a sustainable option such as FCV as an alternative to car use.
In early 2000, FCV and hydrogen-based vehicles created technical interest and had the capability to influence the general public acceptability. FCV and hydrogen-based vehicles are a practical change to be seen as the radical technology in future, and thus, the potentially recognized area still requires in depth research on its acceptability. On the other hand, electric vehicles are also playing a significant role and helping in carbon reduction but currently research emphasizing the acceptability of electric vehicles is still inadequate. Morton et al. [32] identified the opportunities and barriers to the acceptability of electric vehicles at the individual level. Different researchers found different predictors of acceptability to sustainable transportation. Steg and Tertoolen [33] described that habit of car usage has a negative effect on acceptability to sustainable transportation. Steg [25] found out that younger citizens have a negative attitude towards acceptability to sustainable transportation and their usage of the car is positively associated with symbolic and affective motives. Dill and Voros [34] explained that heavy traffic on the road strongly pushes citizens to adopt sustainable transportation options like cycling, especially in European countries. Chatterton et al. [35] identified carbon emission and awareness of climate change as strong predictors of personal transportation choice. Fishman et al. [36] indicated that fear and risk of accident with motorized vehicles is increasing bicycle riding in Australia. Jakovcevic and Steg [37] described that individual norms have a strong influence on the choice of sustainable transportation options. Kim, Schmöcker, Bergstad, Fujii and Gärling [27] pointed out that trust in the government and environmental problem awareness are strongly associated with acceptability to sustainable transportation. Van Acker et al. [38] developed a comprehensive model to show the main predictors of acceptability to sustainable transportation including lifestyle, status, attitude, speed, price, and comfort. Xia et al. [39] found out traffic problem awareness and benefits of sustainable transportation awareness to be strongly associated with acceptability to sustainable transportation. More details about predictors of acceptability to sustainable transportation are given in Table 1.  Based on the above-mentioned literature and Table 1, this study proposes the following hypotheses: Hypothesis 1a. Sustainable transport benefits awareness is positively associated with the acceptability of sustainable transportation.
Hypothesis 1b. Traffic problem awareness is positively associated with the acceptability of sustainable transportation.
Hypothesis 1c. Government policies are positively associated with the acceptability of sustainable transportation.
Hypothesis 1d. Symbolic motives of the car are negatively associated with the acceptability of sustainable transportation.

Hypothesis 2.
Predictors of acceptability to sustainable transportation (Sustainable transport benefits awareness, traffic problem awareness, government policies and symbolic motives of the car) are significantly associated with environmental concern.

Environmental Concern and Acceptability to Sustainable Transportation
Transportation scholars have been inclined to focus on personal beneficial results relating to the perceived time of journey, costs, and flexibility [52], but considering environmental protection is also mandatory for transportation users [53]. A number of researchers have found that environmental concern has a significant influence on travel mode decisions [54,55]. Numerous transportation factors influence environmental concern including apparent threats of environmental destruction to the society, individual, or the earth [56][57][58][59]; concerned responsibility or emotional state of guiltiness for the environmental problem; willingness in the reduction of car use for decreasing the environmental problem [60]; perceived benefits and barriers to sustainable travel behavior [61]. Therefore, based on the above literature, the proposed hypothesis can be as follows: Hypothesis 3. Environmental concern has a positive effect on the acceptability to sustainable transportation.

Mediating Role of Environmental Concern
Previous research has considered environmental concern as an attitude towards environmental problems. Many researchers investigated the relationship of environmental concern with different antecedence and consequent behavior. Several studies indicated that people having high environmental concern are more motivated towards pro-environment behavior [62][63][64][65]. Environmental concern is influenced by different individual, group and institutional factors including demographic variables (gender, age, education, job status), pro-environmental beliefs (e.g., concern for environmental degradation), and institutional (Banks, Federal and local Government, Municipalities) efforts to protect the environment [66]. In this scenario, different pro-environmental beliefs like traffic problem awareness, sustainable transportation benefits awareness, and government policies about environmental protection can trigger environmental concern that ultimately can increase the likelihood of acceptability towards sustainable transportation modes. Therefore, based on the previous literature and this rationale, it can be hypothesized that: Hypothesis 4a. Environmental concern mediates the relationship between sustainable transport benefits awareness and acceptability to sustainable transportation.
Hypothesis 4b. Environmental concern mediates the relationship between traffic problem awareness and acceptability to sustainable transportation.
Hypothesis 4c. Environmental concern mediates the relationship between government policies and acceptability to sustainable transportation.
Hypothesis 4d. Environmental concern mediates the relationship between symbolic motives of car and acceptability to sustainable transportation.

Moderating Role of Self-Transcendence
Self-transcendence integrates two values including universalism and benevolence. People adopting benevolence are kind towards others and try to improve people's interest. Universalism focuses on securing people's interest and nature. People adopting universalism are more inclined towards justice for all and are more impulsive about environmental problems. Therefore, people having high self-transcendence, value society's welfare and focus on collective interest rather than protecting self-interest [67]. Self-transcendence gives a realization about a behavior that is beneficial for the whole of society and makes people more determined to act and follow that behavior. As sustainable transportation promises benefits for both society and nature, it fulfills the self-transcendence consumer's desire to take care of people's interest and nature. Thus, consumers with high self-transcendence are willing to accept sustainable transportation behavior and consumers with low self-transcendence can accept sustainable transportation behavior under external pressure. Hence, it can be hypothesized: Hypothesis 5a. Citizens having high sustainable transport benefits awareness and high self-transcendence values are highly associated with acceptability of sustainable transportation.
Hypothesis 5b. Citizens having high traffic problem awareness and high self-transcendence values are highly associated with acceptability of sustainable transportation.
Hypothesis 5c. Improved Government policies about sustainability and high self-transcendence values are highly associated with acceptability of sustainable transportation.
Hypothesis 5d. Citizens having high symbolic motives of the car and high self-transcendence values are negatively associated with acceptability to sustainable transportation.

Moderating Effect of Self-Enhancement
Schwartz combines two basic values into self-enhancement including power and achievement. Power values focus on the attainment of social status, power and wealth, and enjoying popularity in public. Achievement values emphasize the manifestation of personal achievements in front of others, having the objective to act aggressively and influence others behavior [20]. Self-enhancement values can be influenced by subjective norms during the consumer decision-making process. Subjective norms indicate the external pressure influencing other people in the decision-making process. Consumers favoring other beliefs are more sensitive to external pressure. Consumers having high self-enhancement values are more concentrated on self-interest and personal achievements while neglecting the collective interest [67]. Therefore, the subjective norm has a little role in self-oriented people's lives and shaping their behavior. Contrarily, people having high self-enhancement make efforts to prove their competency and aggressively pursue all alternatives to achieve their targets.
In China, people having certain knowledge, wealth, power and time are more interested to own a car. Thus, this behavior is a signal of consumer competence and a sense of self-enhancement and have a negative attitude towards acceptability to sustainable transportation [68]. So, it can be hypothesized: Hypothesis 6a. Citizens having high sustainable transport benefits awareness and high self-enhancement values are negatively associated with acceptability to sustainable transportation.
Hypothesis 6b. Citizens having high traffic problem awareness and high self-enhancement values are negatively associated with acceptability to sustainable transportation.
Hypothesis 6c. Government policies about sustainability and high self-enhancement values are negatively associated with acceptability to sustainable transportation.
Hypothesis 6d. Citizens having high symbolic motives of the car and high self-enhancement values are negatively associated with acceptability to sustainable transportation.
The model for the study is divided into two parts, model 1 ( Figure 1a) shows the mediation-based model and model 2 ( Figure 1b) shows the moderation-based model. The model for the study is divided into two parts, model 1 (Figure 1a) shows the mediationbased model and model 2 (Figure 1b) shows the moderation-based model.

Methodology
The objective of this study is to explore the attitude of Chinese citizens towards sustainable transportation and to find what can be different predictors affecting willingness to adopt different environmentally friendly sources of sustainable transportation like cycling, hybrid car, hydrogen, and

Methodology
The objective of this study is to explore the attitude of Chinese citizens towards sustainable transportation and to find what can be different predictors affecting willingness to adopt different environmentally friendly sources of sustainable transportation like cycling, hybrid car, hydrogen, and FCV. This study was conducted in four major metropolitan cities of China including Beijing, Shanghai, Guangzhou, and Xi'an. Initially, local traffic management authorities of relevant cities were contacted considering the ethical dilemma of the research. The survey was self-administered and online interviewing using the most popular social apps in China, like WeChat, Weibo and QQ. The target population was from four main cities of China above 18 years old. According to the nature of the study, the sample size is unknown. Ref. [69] suggested a formula to calculate the optimal sample size: The minimum sample size for SEM suggested by different researchers [70][71][72] is 200 and the average percentage of response rate in previous studies related to sustainable transportation is 48% [39,73,74] which is comparatively good. Based on the above suggested values, the sample size of this study can be calculated as: [(200 × 100) ÷ 48] = 417. The data was collected by using a convenient sampling technique. Finally, a total of 800 questionnaires were successfully distributed among the respondents-486 were sent back due to incomplete response, 461 questionnaires were usable, and the response rate was 58% which was enough good to perform structural equation modeling [75]. Five graduate students were recruited to facilitate the data collection. Data were collected from June 2017 to August 2017. Offline and Online, both modes were used to expedite the data collection process. Before data collection, basic information about sustainable transportation and study objectives was provided to respondents. Considering the different types of respondents, respondents were asked to choose between offline and online modes of data collection. Most of the old age respondents preferred to give responses through offline mode. However, most of the respondents decided to use online mode as 650 million of the total population is using different social networks [76]. For online data collection, initially, a web-link including general and variable questions was generated through a survey facilitation website, and then different respondents were recruited randomly on central locations of the cities by adding their social accounts (WeChat, Weibo and QQ). Chinese multi-purpose messaging and social media app WeChat was used to compensate respondents of study by using one of its famous options of money transfer "Hong Bao" to get maximum response rate. Each respondent was compensated with "Hong Bao" at the time of successful completion of a questionnaire that helped to increase the response rate. Details of the respondents are given in Table 2.
The questionnaire was composed of two parts. The first part includes different demographic questions like gender, age, education, work status and general citizen's transportation practices (car use frequency, other transport use frequency, usage of bicycle). The second part includes the questions related to the main variables in the study. Measures for sustainable transport benefits awareness (6-items), traffic problem awareness (4-items) and acceptability to sustainable behavior (5-items) were adopted from the literature [48,50,77]. Measures for government policy (3-items) were adopted from the study of Khoo and Ong [40]. Environmental concern was measured with four items using the scale of Kim, Schmöcker, Bergstad, Fujii and Gärling [27]. Lastly, the symbolic motives of the car were measured with five items using the scale of Steg [25]. All the measures were assessed by using a five-point Likert scale ranging from 1 = Strongly Disagree, to 5 = Strongly Agree. For measures of self-transcendence and self-enhancement, this study adopted the well-established Schwartz's Portrait Value Questionnaire (PVQ) which has been validated in different cultures and translated into many languages [78,79]. A verbal portrait-based short-version of PVQ comprising of 21 imaginary persons was used. Each portrait was rated on a five-point scale where 1 = not like me at all, 5 = very much like me. All the adopted scales were in the English language that is not the official language in China and there is a low percentage of Chinese citizens who have a good ability to understand English [80]. All the questions were translated into Chinese language and then sent to two language experts of Xi'an international studies university to check its content validity. After performing three repetitions, a structured translated version of the questionnaire was obtained.

Analysis
Finally, 486 questionnaires were received, due to incomplete response, 461 questionnaires were usable. Validity and reliability analysis were examined by Exploratory factor analysis (EFA) and Confirmatory Factor Analysis (CFA). Internal consistency was checked by Cronbach's Alpha; Cronbach's Alpha values ranged from 0.78-0.93, which demonstrates internal consistency of all six constructs is greater than the recommended value of 0.70, as recommended by Ref. [81]. Values of Cronbach's Alpha exhibits that the developed scale is reliable.
Exploratory Factor Analysis (EFA) was applied to discover the latent variable on six constructs containing 27 items. The main objective of EFA was to identify the relationship between latent and observed variables if the variables are uncertain and unknown [82]. In this study, principle comments analysis with varimax rotation was applied to implement EFA on 27 items. Exploratory Factor Analysis begins with analyzing the suitability of data through sampling adequacy Kaiser-Meyer-Olkin (KMO) and Bartlett test. According to the criteria, the value of KMO should be 0.60 or more to perform factor analysis [83]. The value of KMO was 0.816 which meets the criteria and the outcome of the Bartlett test was X 2 = 3124.567 and p > 0.000 that is representing significant and sufficient inter-correlation. Dabholkar et al. [84] suggested the factor loadings of all items should be more than 0.40. According to Hair et al. [85], the value of commonalities and cross-loadings should be greater than 0.40 to meet the criteria. According to the findings of EFA eigenvalues, all six constructs should be 1 or more than 1 as suggested by Kaiser [86]. All the factors have an eigenvalue more than 1 with 71.56% total variance. The values of factor loading were ranging between 0.52-0.85 which meets the above-mentioned criteria. Therefore, no item was deleted from the study. The results for EFA are presented in Table 3. Finally, Confirmatory Factor Analysis (CFA) was applied to 27 items in six categories for the purpose of judging constructs validity. AMOS 21 statistical analysis software was used to perform CFA research technique of Structural Equation Modeling (SEM). CFA is the one of the most important research techniques of SEM, which is widely used in different studies of transportation to find the covariance structure [87] or linear structural relationship models [88]. When a researcher has inadequate information related to latent factors, multivariate regression is used to find the significant relationships between factors. Twenty-seven items under six categories of the confirmatory model were scrutinized, applying different kinds of model fitness indices. The findings of the model displayed that squared multiple correlation (SMC) values ranged between 0.489-0.735, which meets the criteria.
The final results of CFA, model fitness and correlation among different variables of the study are shown in Tables 4 and 5.

Results of Hypothesis
As recommended by Muller et al. [94], this study utilized a hierarchical multiple regression to check the hypothesis, mediation, and moderation. Moreover, following the guidelines of Zhao et al., this study confirmed mediating and moderating effects by running scripts to check the interaction and indirect effects [95][96][97][98].
The results of the study were categorized on the base of mediation and moderation results. As Table 6 describes results for the mediation model and Table 7 presents the results for moderation analysis.
Model 1 and Model 3 in Table 6 introduced control variables influencing acceptability to sustainable transportation. Model 2 (Hypothesis 1) proposes a significant association between sustainable transportation benefits awareness, traffic problem awareness, government policies, symbolic motives of car usage and environmental concern. The results show a significant positive association between sustainable transportation benefits awareness and environmental concern (p = 0.000); traffic problem awareness and environmental concern (p = 0.021); government policies and environmental concern (p = 0.082). However, symbolic motives for car usage are not associated with environmental concern (p = 0.431).
Model 4 (Hypothesis 3) proposes a significant association among sustainable transportation benefits awareness, traffic problem awareness, government policies, the symbolic motive of car usage and acceptability to sustainable transportation. The results show a significant positive association between sustainable transport benefits awareness and acceptability to sustainable transportation (p = 0.005); traffic problem awareness and acceptability to sustainable transportation (p = 0.0023); and government policies and acceptability to sustainable transportation (p = 0.0000). However, the symbolic motive of car usage is not associated with acceptability to sustainable transportation (p = 0.753).
Model 5 (Hypothesis 4) proposes a significant association among sustainable transportation benefits awareness, traffic problem awareness, government policies, the symbolic motive of car usage and acceptability to sustainable transportation via environmental concern.
PROCESS macro with bootstrapped confidence interval [95,96] was used to check the mediation effect due to superiority over other mediation methods like the SOBEL test [95]. Mediation analysis was performed using 10,000 bootstrap samples & 95% confidence interval (CI). If the values of the lower and upper 95% CIs are either both below or both above zero, mediation works. The results show the mediating role of environmental concern in between sustainable transport benefits awareness and acceptability to sustainable transportation (p = 0.025); as well as traffic problem awareness and acceptability to sustainable transportation (p = 0.010). However, environmental concern is statistically not mediating among government policies and acceptability to sustainable transportation (p = 0.573) as well as the symbolic motive of car usage and acceptability to sustainable transportation (p = 0.743). The results for mediating the role of environmental concern are described in Table 6. Next, we tested H5 and H6 according to the guidelines of Hayes and Matthes [97] for determining the moderating effect in a model. Control variables and direct variables were again introduced in M1* and M2* respectively. While the moderating variable of self-enhancement was introduced in model 3* (Hypothesis 5), according to results, self-enhancement is negatively moderating among sustainable transport benefits awareness and acceptability to sustainable transportation (p = 0.002), and government policies and acceptability to sustainable transportation (p = 0.000). However, self-enhancement is positively moderating among traffic problems awareness and acceptability to sustainable transportation (p = 0.956) and the symbolic motive of car usage and acceptability to sustainable transportation (p = 0.754).
Model 4* (Hypothesis 6) proposed self-transcendence is positively moderating among sustainable transport benefits awareness and acceptability to sustainable transportation (p = 0.005) as well as to government policies awareness and acceptability to sustainable transportation (p = 0.0001). However, self-transcendence is statistically not significantly moderating among traffic problem awareness and acceptability to sustainable transportation (p = 0.865) and the symbolic motive of car usage and acceptability to sustainable transportation (p = 0.902).
In model 5*, the combined moderating effect of self-enhancement and self-transcendence was evaluated. However, the results remain the same.
To analyze the moderating effect of self-enhancement and self-transcendence, this study utilized the MODPROBE macro in Statistical Package for the Social Sciences (SPSS) as suggested by Hayes and Matthes [97]. MODPROBE is a widely applicable technique to check the moderating effect in a structural model. Taking sustainable transport benefit awareness, traffic problem awareness, government policies related to sustainability, symbolic motives of car usage as independent variables, self-enhancement and self-transcendence as moderating variables, and acceptability to sustainable transportation as the dependent variable, results for moderation were obtained. Five-thousand bootstrap resamples were used to create the statistical output in MODPROBE. The conditional effects of self-enhancement and self-transcendence were determined at values of one standard deviation (SD) below the mean at the mean, and one SD above the mean. The results for moderating effects can be found in Table 7. Table 7. Regression Results (Moderation).
According to Cohen et al. [99], the simple slope test provides more details about the interacting role of moderators. This test judges whether the association between independent variables (X) and the dependent variable (Y) is significant at a specific value of moderating variables (Z). Jeremy Dawson developed an excel-based worksheet to conduct the simple slope test. Therefore, according to the recommendation of Dawson [100], this study utilized Jeremy Dawson's Excel worksheet to perform a simple slope test and to show moderating effects at low and high values (STBA*SE, TPA*SE, GPS*SE, SMC*SE, STBA*ST, TPA*ST, GPS*ST, and SMC*ST) on acceptability to sustainable transportation. Slope significance results at high and low values were created by "Two-way interaction effect" excel worksheet [101]. Figures 2-9 present the slope analysis of moderating results of self-enhancement and self-transcendence between predictors and acceptability to sustainable transportation. In Figures 2 and 4, the negative moderating effect of self-enhancement is found between STBA and AST; GPS and AST. recommendation of Dawson [100], this study utilized Jeremy Dawson's Excel worksheet to perform a simple slope test and to show moderating effects at low and high values (STBA*SE, TPA*SE, GPS*SE, SMC*SE, STBA*ST, TPA*ST, GPS*ST, and SMC*ST) on acceptability to sustainable transportation. Slope significance results at high and low values were created by "Two-way interaction effect" excel worksheet [101]. Figures 2-9 present the slope analysis of moderating results of self-enhancement and self-transcendence between predictors and acceptability to sustainable transportation. In Figures 2 and 4, the negative moderating effect of self-enhancement is found between STBA and AST; GPS and AST.

Discussion
This study reveals that Chinese citizens are more dependent on personal vehicles due to concerns about safety in public transport. They have a negative perception towards the public transport system. Our findings show that citizens having awareness about traffic problems and sustainable benefits of transport are willing to accept sustainable transport options. These findings are also consistent with the studies of Banister and Button [102] and Franzen [103]. Consumers having more awareness about traffic and sustainability issues nowadays is due to the heavy focus on awareness campaigns in China. China Ministry of Transportation initiated a development plan in 2015, and according to this plan, one out of three citizens must use public transportation rather than using his own car to protect the environment and to get rid of transportation problems. Chinese mayors are also encouraging local citizens to use green buses rather than using own cars.
However, symbolic use of a car is negatively associated with acceptability to sustainable transportation which contradicts with findings of Bergstad et al. [104]. As Chinese citizens are getting wealthier and the automobile has become a lucrative market; therefore, luxury lifestyle and shining cars captured their attention and they are less likely to adopt sustainable transportation. According to Stern [105], awareness of environmental issues and desire to reduce these issues are main predictors

Discussion
This study reveals that Chinese citizens are more dependent on personal vehicles due to concerns about safety in public transport. They have a negative perception towards the public transport system. Our findings show that citizens having awareness about traffic problems and sustainable benefits of transport are willing to accept sustainable transport options. These findings are also consistent with the studies of Banister and Button [102] and Franzen [103]. Consumers having more awareness about traffic and sustainability issues nowadays is due to the heavy focus on awareness campaigns in China. China Ministry of Transportation initiated a development plan in 2015, and according to this plan, one out of three citizens must use public transportation rather than using his own car to protect the environment and to get rid of transportation problems. Chinese mayors are also encouraging local citizens to use green buses rather than using own cars.
However, symbolic use of a car is negatively associated with acceptability to sustainable transportation which contradicts with findings of Bergstad et al. [104]. As Chinese citizens are getting wealthier and the automobile has become a lucrative market; therefore, luxury lifestyle and shining cars captured their attention and they are less likely to adopt sustainable transportation. According to Stern [105], awareness of environmental issues and desire to reduce these issues are main predictors of pro-environmental behavior. More awareness about the transport problems makes the citizens more environmentally concerned and it is also consistent with the results of Kim, Schmöcker, Bergstad, Fujii and Gärling [27]. This study revealed that sustainable transport options can be experienced due to environmental consciousness, whereas positive changes in the environment can be seen gradually due to the adaptation of sustainable transport options.
The results show the medium mediating effect of environmental concern in between sustainable transport benefits awareness and acceptability to sustainable transportation, traffic problem awareness and acceptability to sustainable transportation. These results are consistent with the application of NAM as a mediation model, as environmental concern is triggered by sustainable transport benefits awareness and traffic problem awareness [25,106]. It also confirms the rationale of earlier studies that environmental concern has a strong impact when ascription of responsibility related to traffic problems leads to the acceptability of sustainable transportation behavior [107,108]. However, the mediation effect can variy from context to context and depends on earlier knowledge of consumers related to transportation issues.
This study also proved the significance of personal values shaping sustainable transportation behavior as self-enhancement is negatively moderating the acceptability of sustainable transportation which also verifies the results of Schultz and Zelezny [26]. The moderating role of self-transcendence is also proved as consumers are willing to go for green for general society and these results are also consistent with the study of Jakovcevic and Steg [37]. However, still, the adoption of sustainable and green public transportation is at the infancy stage due to multiple barriers.
Making public transport a safe option for Chinese citizens should be the priority policy of the government. An effective marketing program should be developed to create awareness about sustainable transport options. Negative impacts of the car should be communicated to reduce car usage; although this study suggests that citizens having environmental concern are less likely to use the car and adopt sustainable transport options. Moreover, this study authenticated the importance of traditional modes of sustainable transportation such as cycling. Citizens having bicycles are more likely to reduce car usage than non-bicycle ones. Although citizens use car five times in a week for traveling, the bicycle is still considered a good solution for recreation and exercise. Therefore, recreational cycling should be shifted towards commuting cycling.

Practical Implications
The results of this paper have a potential implication for the government of China, transportation, and urban planning departments. According to respondents, an adaptation of public transportation and cycling is unsupportive because of risky and time-consuming modes of transportation. Moreover, public transportation is not reliable and is more congested. It could be a significant barrier for adaptation of sustainable modes of transportation and reduction in the usage of cars. Therefore, to increase the acceptability of sustainable transportation, an improved strategy should be developed with the integration of transportation, land and urban planning departments. To achieve more positive results, stakeholders' involvement should be given key priority at the time of strategy formulation and implementation.
Different measures can be taken by the government to reduce the car usage among citizens. Therefore, incentives-based policy should be introduced to increase the acceptability of sustainable transportation among citizens. Discounted fares on green buses and metro trains can be offered to increase their usage. Policy makers and planners should be encouraged to reduce driving cars and motivate the public to adopt sustainable transportation options. A pollution-free environment through a reduction in car usage is considered as a best practice to create sustainability in the world by focusing on the biosphere, and altruistic and hedonic advantages [109,110]. The relevant authorities should create awareness among citizens about low car usage and highlight its advantages including sustainable biospheres, reduction in the emissions of CO 2 , and reduction in noise and smog. Alternative modes of active transportation (sustainable electric vehicles like green buses and Metro trains, FCV, cycling, and walking) should be encouraged by highlighting the benefits of sustainable transportation to enjoy good health and better fitness. Hedonic motives of sustainable transportation can be highlighted to increase affection towards it. The Media has an important role to create awareness, but a strong collaboration between media and traffic control authorities is needed to promote sustainable transportation. OFO and MOBIKE are two leading Chinese bike-sharing companies in China with 2 billion in capital. Their motive is to provide sustainable and pure environmentally friendly mode of transportation. Although, Chinese bike sharing companies are trying to promote environmentally friendly behavior in Chinese citizens, they are also creating difficulty in traffic control. Shortage of parking slots and low awareness about parking bikes at an appropriate place is also increasing problems. Therefore, improvement in regulation should be made for better and effective utilization of sustainable transportation options. According to our findings, it is necessary that personal norms must be strengthened by creating awareness among Chinese citizens about problems associated with usage of cars and to try to increase the sense of responsibility to stimulate their personal norms and values to increase the acceptability level. We believe our study can give new intuitions to increase the personal acceptability and will have a positive effect on the policies of sustainable transportation in major cities of China like Beijing, Shanghai, Guangzhou, and Xi'an.
This study also has the potential to foster sustainable transportation across cultures to strengthen personal norms and values. However, absolute values can be compared to studies on main variables if structural and cultural differences affect them. For example, awareness of the consequences will be greater in that city or country where the usage of cars is affects the environment more, and personal norms will be weaker in that city or country like China where the usage of alternative modes of transportation is not so good, for example: Having no respect for cyclists and trains; subways suffer daily from delays and excessive crowding; and there is no availability of a proper local transportation system. In this case, it will be a difficult task to reduce the car usage.

Concluding Remarks
Public transport and other sustainable transport options like cycling are eco-friendly alternatives to car use. This study developed an empirical model of acceptability to sustainable transportation in China. The results of the study highlight the benefits of the sustainable transportation options and have proposed a sustainable solution to transportation problems in China. The government must take initiatives to reduce car use and divert the citizens to choose sustainable modes of transportation. Transport policy measures should be the first priority to reduce environmental problems. However, designing environmentally friendly policy is not sufficient, a variety of educational workshops and seminars should be conducted periodically to reduce car use. Media should play a positive role to create awareness about transportation problems and to provide information on sustainable alternatives of transportation.
This study was based on a cross-sectional survey, however, behavioral changes in respondents are still unknown. Secondly, the study was conducted in four major cities of China and the results were interpreted altogether. This being said, results may differ in between these four cities due to the difference in car ownership rate, public transport infrastructure, urban development, and perception of sustainable transportation. Therefore, comparing the acceptability of sustainable transportation behavior in major cities of China can be a potential focus of future research. Moreover, future research can be conducted to make a comparison of the sustainable behavior of Chinese citizens with other developed nations. Other researchers may be interested in exploring the risks associated with public transportation in China. A comparison of public and personal transportation effectiveness can be a