Private household demand for vehicles on alternative fuels and drive trains: a review

Abstract

Purpose

Any attempt of the government to encourage the purchase of vehicles on alternative fuels and drive trains will depend on the acceptance of the end-users on the demand side. This paper offers an in-depth understanding of the consumers’ attitudes and preferences towards AFVs which can guide the government to establish effective policy measures.

Method

A comprehensive review of research is performed under different conceptual frameworks and research methodologies: attitudinal, experimental, preference valuation studies and others. Research findings are reported with the general objective to (1) uncover the attitudes and preferences towards AFVs and (2) examine whether the environmental benefits of AFVs play a role in the car purchase decision.

Results

Overall, there exists a strong environmental concern, and positive attitudes towards AFVs. However, environmental benefits are of little importance in the car purchase decision, which is principally driven by price characteristics, performance and convenience attributes. Limited knowledge levels also seem to prevent building up awareness of AFVs, which is the key to their adoption.

Conclusions

The adoption of AFVs is likely to be limited without significant governmental incentives and regulations. Based on the key findings, it can be recommended that a combination of educational campaigns (e.g., information tools), pricing measures (e.g., differentiated vehicle taxation), supply-sided measures and large-scale demonstrations is required to support the adoption of AFVs.

1 Introduction

Two important factors have caused major evolutions and developments in the transportation and automotive sector and have stimulated the use of new technologies for our transportation models: the availability of energy sources and the important adverse effects of transportation systems on the environment [93]. The finite nature of oil resources and the associated political and economic effects presently lead to the need of assessing alternative energy sources and to reduce the dependence on imported oil. In addition to these energy aspects, the transportation sector is responsible for a substantial part of pollutant emissions in the atmosphere, which are directly and indirectly impacting different receptors such as people, material, agriculture, climate and ecosystems [92]. To reduce the harmful emissions and to make the use of finite energy sources more efficient, effective policy measures need to be installed by the relevant authorities. One effective approach to attain these objectives is to reduce the use of personal transportation by encouraging the use of the bicycle and public transport [73]. However, most consumers are not inclined to let go their primary means of transportation, mainly because of strong feelings of convenience and independence associated with car use [7]. Therefore, encouraging the purchase of alternatives to conventional petrol and diesel vehicles is essential. Vehicles on alternative fuels such as liquefied petroleum gas (LPG), compressed natural gas (CNG), biofuels and hydrogen and drive trains such as electric vehicles (EVs), (plug-in) hybrid electric vehicles ((P)HEVs) and hydrogen fuel cell vehicles (HFCVs) offer an attractive solution to reduce the environmental impact of the vehicle fleet [48].

A large scale adoption of these AFVs is a great challenge. It depends not only on large-scale infrastructure costs, such as refuelling and recharging facilities on the supply-side, but also on the acceptance by the end-users on the demand side. It is now widely recognised that each attempt to change the consumers’ activities and lifestyles requires a sound knowledge of preferences and determinants of consumer demand [75]. In this respect, unveiling the consumers’ attitudes and preferences towards AFVs is necessary for the formulation of effective policy measures.

Literature on the potential demand for AFVs has mainly emerged since the late 80s and has been studied under very different conceptual frameworks. This paper conducts a comprehensive literature review and presents a classification scheme to map and uncover (1) the preferences and attitudes towards AFVs and (2) whether their environmental benefits can become a new dimension of vehicle choice by consumers. Section 2 outlines the search strategy, whereas Section 3 presents the main findings of the literature review according to the applied conceptual framework and research methodology. Section 4 concludes and provides policy recommendations.

2 Search strategy

According to Cooper [28], a research review should be designed in a systematic, objective way. To this extent, the integrative research review consists of several stages. The first stage is the formulation of the research question(s), which will guide the research. Here, the aim is to uncover consumer preferences for AFVs and to examine whether the environmental benefits of AFVs play a role in the car purchase decision. The second stage is the determination of the data collection strategy and a selection of multiple channels in order to avoid a bias in coverage (Section 2.1). The third stage, elaborated in Section 2.2, provides an evaluation and selection of the retrieved data. The fourth stage contains an analysis and interpretation of the reviewed literature (Section 2.3) which finally leads to the presentation of the results (Section 3) [19].

2.1 Data collection strategy

The data collection strategy is based on a computerised search. Articles were mainly retrieved by tracking cited references from e-catalogues. The reviewed papers were published mainly since the last two decades. Several sources were used to search for literature. These included the web-based search tools (V-spaces, article database; “web of science” and other e-sources) and the VUBIS e-catalogue from the library of the Vrije Universiteit Brussel (VUB). In addition, web-search robots (e.g., Google Scholar) were used to track cited references and to find publication titles, using the search term ‘alternative fuels and drive trains’ combined with ‘purchase behaviour’, ‘private household demand’, ‘environment’ and ‘consumer preferences’. From the resulting output, the relevant hits were filtered out based on their publication in peer-reviewed journals, citation index (Min. 1, except for recently published articles, see Table 1) and their focus on the purchase of AFVs by private households.

Table 1 Citation indices of the retrieved peer-reviewed articles

2.2 Evaluation of the retrieved data

By using the above described strategy, 53 publications have been retained for further analysis. First, the retrieved data show divergences according to the applied conceptual framework and research methodology (see Table 2). They can be grouped into attitudinal, experimental, preference valuation and other studies. The majority of the collected articles applied preference valuation techniques (27), followed by attitudinal surveys (14), experimental designs (8) and others (4). Many articles involve a combination of them. Especially attitudinal surveys are often used in a first phase to develop the survey instrument or to obtain in-depth information about the consumers’ attitudes on environmental issues. Second, research from the 80s and 90s mainly focused on the potential demand for battery EVs [13,14,24,27,38,39,54,55,79,90], while studies from the late 90s and 2000s rather address a mix of AFVs including EVs, LPG, CNG or methanol [21–23,33,34,42,81,87]. In line with technological developments, recent research also concentrates on HEVs [3,10,26,29,31,32,45,49,53,72], PHEVs [9,11], biofuels [51,68,69,80,89,91], hydrogen [2,66,74,76,86] and HFCVs [46,61,62,65]. Finally, most literature has been published in America. Out of the 53 reviewed articles, 19 were carried out in California, 10 in other US states and 7 in Canada. Europe is represented with 16 articles and Asia with 1 article. The bias towards California as the geographical focus of attention could be attributed to the heightened awareness of air pollution due to local conditions and press attention [37,87], its importance in global HEV sales (25 % of total US sales in 2006) [45], the low-emission vehicle regulations and state programs [39,87] and the highest count of Green Party registered voters throughout the US [53]. Only recently, European studies have gained in number, especially in the field of attitudinal surveys and preference valuation techniques.

Table 2 Evaluation of the retrieved data

2.3 Analysis and interpretation of literature

Based on the evaluation of the retrieved data, the research findings will be treated according to the applied conceptual framework and research methodology (see next Section 3).

3 Results

In the following subsections, the conceptual frameworks and research methodologies are briefly described and an overview of common cited critics is given. Then, the major findings are listed and general themes and response patterns are observed.

3.1 Attitudinal studies

Attitude theory [30] is a central concept in environmental psychology and typically relates attitudes to behaviour through an intermediary intention construct. One of the most applied theories to study behaviours of environmental relevance is the theory of planned behaviour (TPB) [5]. This theory stipulates that behavioural intention is shaped by attitudes towards the specific behaviour (overall evaluation of its possible consequences), subjective norms (the perception of a person about the normative expectations of others such as close friends or family) and perceived behavioural control (PBC) (personal feeling that one could easily change its behaviour and that one has the possibilities to do this). TPB pretends that if attitudes and subjective norms are favourable, the PBC will be larger and the intention for behavioural change will be stronger [4,5]. In this context, the adoption of an AFV will be immediately influenced by a person’s intention to adopt the technology. Other conceptual frameworks in the field of environmental psychology include the norm-activation model (NAM) (by [77,78]), which focuses on moral values and personal norms to explain (altruistic) behaviour, and the value-belief-norm (VBN) theory (by [83,84]) to explain commitments to protect the environment.

Methodological approaches to measure the correlation between attitudes and behaviour in environmental psychology often apply quantitative methods, qualitative methods (e.g., semi-structured interviews, focus groups, group discussions etc.) or a combination of both.

Although the TPB and other theories are well tested, they rely on complicated links between consumer values, knowledge, beliefs, attitudes, intentions and behaviour. A large size of factors is often difficult to quantify, predict and manage and even if they are known, there is a loose causal link between intentions and actions. The explanatory value of attitudes on behaviour is thus limited, but might enlarge when behaviour measures are self-reported, than when observed [8,75]. In addition, the choice of survey questions might be subjected to potential biases (e.g., framing, sample selection bias etc.). Quantitative surveys might for example provide less opportunity to let people frame their own public perceptions and attitudes than qualitative surveys, but the latter encounters the limitation of being representative for wider populations [74].

Table 3 shows an increasing emergence of attitudinal surveys within the last 7 years, mainly executed in Europe. Except for Ricci et al. [74] and Schulte et al. [76], quantitative surveys were applied to reveal the consumer preferences for AFVs. Within the surveys, there is a predominance of measuring the attitudes towards hydrogen [2,66,74,86] and biofuel vehicles [69,89,91]. Overall, the general concern about environmental issues is found to be high (general positive environmental attitudes), but very often, this is not translated into changes in purchasing behaviour [2,66,74,94]. This discrepancy between environmental attitudes and ecological behaviour is known as the attitude-action gap [56]. Most of the reviewed studies have addressed this attitude-action gap and have consistently reported two findings.

Table 3 Reviewed attitudinal studies

First, attitudes and behaviour towards AFVs are not merely determined by environmental considerations, but are the outcome of a complex trade-off involving economic [69,74,89], performance [66,74,86] and psychological factors [67] including less conscious determinants such as status [52] and symbolic motives [67]. Moreover, individuals will rather value the environmental benefits of AFVs in terms of potential monetary savings, than out of environmental concern [69,89].

Second, limited knowledge levels currently prevent to build up awareness of AFVs, which is the key to their adoption [66,74,86]. Prior levels of AFV knowledge and hence awareness are found to be associated with socio-demographic (e.g., gender, age) and personal characteristics (e.g., education) [66,86], environmental knowledge [35,66,86,94], pro-environmental attitudes [35,86], cultural dispositions [2], product involvement [66,94], direct experience (e.g., in terms of practical experiences and demonstrations) and familiarity with AFVs [74,94].

Besides attitudes, an increased belief of the ability to influence the environment positively (PBC) is found to affect behavioural change in the same way [67,69,91]. To strengthen the PBC, information is required that focuses on the opportunities and possible solutions (e.g., range of actions that can be taken within car purchase to reduce energy problems), instead of messages that contain negative information and strengthen the seriousness of the problem and its detrimental consequences [66,69,91].

The need for information is a recurrent finding throughout most of the reviewed studies [2,35,66,74,85,91]. Audiences are found to behave differently and require information to be differentiated according to the interests and knowledge levels, socio-demographic characteristics, attitudes and cultural dispositions of the specific target audience [2,74,91,94]. Performance attitudes are found to be positively related to information search [94], whereas people with environmental attitudes are less affected by information provision [91,94]. In this respect, tailored information which focuses on the new technical developments that improve environmental performance while maintaining car performance might for example help to enhance the support for AFVs [94].

3.2 Experimental studies

In experimental and quasi-experimental studies, individuals are put in a natural or an artificial setting to observe their behaviour towards a group of individuals not exposed to the experimental treatment. Experimental studies often make use of vehicle trials or clinics, activity-based approaches, gaming simulations or design spaces [11,55]. Activity analysis includes the use of household travel diaries, activity location maps, videos and other informational material to observe daily travel patterns and understand consumers’ needs with respect to AFVs [55]. Gaming simulations are experimental contexts in which respondents seek solutions to a particular problem or issue (e.g., range limit) within their activity space [40,55]. Design spaces are used to elicit the consumers’ design priorities and preferences of AFVs, which is consistent with theories of constructed preferences that view consumer preferences as outcomes (and not as inputs) of decision contexts and processes [11,15].

Although experimental designs rely on virtual or real-world experiences of the technology and are more realistic than other survey techniques, they have their limitations. Trials may for example evoke the “Hawthorne” effect, indicating that people will produce upward biased estimates of interest in AFVs since they receive special attention. As a result, fewer people than those who expressed a purchase intention are likely to purchase such a car. Additionally, there may arise several measurement problems related to the duration and length of the trial. Trials may also provide reactions to a specific category or product because of the opportunity that the participants have to experience competing technologies (e.g., conventional gasoline cars) [39].

All reviewed experimental studies, displayed in Table 4, were performed in California (US). Many of them were carried out in the 90s to understand how consumers could address EV limitations. In line with technological developments, recent experimental studies rather concentrate on HFCVs and PHEVs. All vehicle technologies included in the experimental designs face driving range and infrastructure challenges and rely on an electric motor powered by a unique fuel source [55,61].

Table 4 Reviewed experimental studies

Most experimental studies shared the opinion that there is a strong concern for the environment, and a strong belief that lifestyle changes are required to solve environmental problems [38,39,54,55,90]. However, they also discovered that the environment was the lowest rate issue when purchasing a vehicle (see for example [55,90]). Although environmental awareness may not lead to the purchase of an AFV, it might encourage households to seek out and evaluate AFVs for purchase considerations [55].

Short-term exposure improves the respondents’ overall impressions of AFVs, especially with respect to their environmental benefits [39,61]. But, as they gain experience with AFVs, those perceived environmental benefits become a lower priority as other vehicle features will enter the decision set [39]. On the one hand, comparisons will be made based on range, purchase price and convenience of use [38]. Some of the reviewed studies reveal that respondents did not change their perception about the desired range [38,39,61]. Despite the demonstrated utility of AFVs, respondents still desire ranges to be similar to that of a conventionally fuelled car, even when travel diaries showed that they were usually travelling less on a daily basis [38,61]. Acceptable driving ranges are found to be 160 km for EVs [38,54] up to 480 km for HFCVs [61]. On the other hand, consumer preferences might emerge with respect to the new qualities of AFVs (e.g., quiet ride, low maintenance costs) [38,54,55]. In this respect, Kurani et al. [55] argue that multi-vehicle households will combine AFVs and conventional vehicles in their stock to achieve the advantages of the different propulsion systems. These “hybrid households” will not be discouraged by the limited driving range of AFVs as they allocate household travel according to the different operational characteristics of the vehicles (i.e., conventional vehicles for longer trips, AFVs for shorter trips). The attractiveness of AFVs will not lie in their competitive, but in their complementary relation to conventionally fuelled vehicles. In addition, Kurani and his colleagues assert that any disutility of reduced range can be more than offset by the value of home recharging [9,11,55]. They stipulate that a succesful market launch of AFVs will not depend on the duplication of the performance attributes of conventionally fuelled vehicles, but on the recognition that there is a potential market for less ambitious AFV designs with shorter driving ranges. According to these authors, the commercialisation of more ambitious AFVs should be inevitably accompanied with financial incentives, large-scale vehicle demonstrations and persuasive information campaigns to overcome the financial barriers and the lack of inherent interest.

3.3 Preference valuation studies

Preference valuation studies are another technique to analyse the potential demand for environmental goods or services which are usually not traded within the market mechanism. Consumer preferences are usually inferred by stated or revealed preference techniques. The stated preference (SP) technique is a survey-based technique that allows researchers to uncover how people value different product/service attributes. The most common SP techniques used in transport studies are the choice modeling (CM) method and the contingent valuation method (CV). CM originates from conjoint analysis, information integration theory in psychology [6] and discrete choice theory in economics/econometrics [58,59]. It applies a choice experiment approach using a variety of instruments (e.g., pencil and paper, computer aided personal survey instrument (CAPI), internet-based survey) to indirectly elicit attribute values based on either ranking or rating of products described by a number of attributes in several labelled or unlabelled choice sets [18,41,47]. Subsequently, via statistical techniques, the analysis will derive a value for each of these attributes and thus express the relative preferences among vehicle attributes [29,79]. Conventional discrete choice (DC) models analyse situations in which respondents are asked to choose one alternative from a set of mutually exclusive hypothetical alternatives [17,50]. Recently, multiple discrete-continuous extreme value (MDCEV) models have been introduced that deal with the existence of multiple-vehicle households, where households own and use multiple vehicles for satisfying their travel needs [16,17]. Other recent progresses in CM aim to improve realism, by for instance adding a no-choice option [31], or by customising attribute levels based on respondent’s current vehicle choices [10,31,62].

In CV, value elicitation is whole-product based by asking respondents to express their maximum willingness to pay (WTP) for a given improvement of a public good provision level (e.g., cleaning up a lake) or for public goods aspects of a market good (e.g., eco-labeled goods) [44,63]. In the dichotomous CV design (yes/no answers), respondents accept or refuse a payment for a change in the quality or the quantity of a good at a given cost, while open-ended questions (such as payment cards and bidding games) provide a way to elicit the respondent’s maximum WTP [63,64]. CV and CM offer rather different merits and their use entirely depends on the purpose of the study under consideration. CM is particularly suited to measure the marginal value of changes in various characteristics of environmental goods and allows a deeper understanding of the trade-offs between attributes, whereas CV is a better technique than CM when the main objective of the study is to value an overall policy package and for assisting in policy evaluations [25,43,44,50].

Economists have been sceptical towards the use of SP data. One possible problem with hypothetical choices is that it may not reflect the real purchase intentions of the respondents (i.e., hypothetical bias) [20,47]. Another criticism is that SP surveys view consumer preferences as inputs to decision contexts and processes and assume that consumers have preferences for attributes that are unfamiliar to them. Consequently, these surveys might not capture the complexity of vehicle purchase behaviour [9,15,39,55]. Moreover, respondents tend to give socially desirable responses, such as “feel good” responses for environmental benefits or they may provide in contrast anti-environmental survey responses [55]. As a result, they may signal their preference for provision of less pollution, although in reality they would not spend any extra money on purchasing an environmentally friendlier car. Ewing and Sarigöllü [34] also point out that people who are highly concerned about the environment may have a higher motivation to return the surveys. Finally, Kurani et al. [55] state that surveys usually question one person from a household, while vehicle purchases are often made jointly by the whole household. In the literature on CV, an extensive overview of potential sources of bias is given by Mitchell and Carson [63], Carson [25], Bateman et al. [12] and Venkatachalam [95], which can also offer guidance on how to cope with potential bias in hypothetical choice experiments [47].

In contrast to the SP technique, the revealed preference (RP) technique uses real market data from observations on actual choices in order to measure the consumer preferences. So RP data or market data do not have the possibility for confusion or unstated assumptions. But the main problem in predicting a market for AFVs by using RP data is the absence of actual choice observations since only a small market share of AFVs is currently available [70,71]. Furthermore, using RP data makes it difficult to observe the effect of large variations in the variables of interest. Finally, RP data may often produce strong correlations between the variables (multicollinearity) and may evoke difficulties in measuring the vehicle attributes [1]. Because SP and RP have complementary strengths, a growing body of literature applies joint SP-RP modeling techniques (e.g., [10,22]).

Except for Brownstone et al. [22] and Axsen et al. [10], all studies, listed in Table 5, applied SP surveys with a predominance of CM, used for the identification of unique attributes of AFVs and their effects on vehicle purchase. All reviewed studies from the 80s and 90s were performed in America and focused on battery EVs or on a mix of AFVs including either EVs, LPG, CNG or methanol. Later research also included HEVs, PHEVs and HFCVs in the vehicle choice experiments. These reviewed CM studies reveal that the most critical factors for the adoption of AFVs are price characteristics (e.g., purchase price, fuel costs) [3,26,29,33,72,79], followed by performance and convenience attributes (e.g., driving range, recharging times, fuel availability) [13,14,21,24,27,29,33,42,72,79]. Although people express a willingness to pay for reduced emission levels [21,23,87], environmental benefits are consistently found to be of minor importance compared to these attributes [26,27,34,72].

Table 5 Reviewed preference valuation studies

Recent studies also apply CM to capture the dynamics in consumer preferences for new technologies [10,31,62]. These studies reveal that conventional vehicles become less desirable with increases in AFV adoption, given equal monetary costs (i.e., neighbour effect) [10,31,62]. However, these dynamics in consumer preferences seem to depend on the type of new technology. Consumers will more likely switch to HEVs than to HFCVs [62] or to EVs [31]. This can be attributed to the fact that HEVs exhibit low switching costs (e.g., no reliance on the availability of charging stations), whereas HFCVs and EVs possess attributes that are unfamiliar to consumers (e.g., driving range) and require technical infrastructure (e.g., to recharge the car at home) [31,62].

A minority of the reviewed SP studies applied the CV method. In recent years, this method was especially applied to unveil the WTP for biofuels [68,80,81], HFCVs [65] and HEVs [32]. Similar to other CV literature, the WTP for AFVs is found to be positively influenced by income [32,80] and environmental concern [32,51,65,80,81]. Despite these levels of environmental concern and supportive attitudes towards AFVs, the WTP is mainly determined by financial considerations. The high initial costs of HEVs currently prevent them from gaining a market share (e.g., in Turkey) [32], the WTP for HFCVs is driven mostly by expectations of personal financial savings (e.g., reduced running costs) [65] and there only exists a WTP for methanol if the cost burden is shared [81].

To widen the acceptance of AFVs, these studies suggest that policymakers should act on the environmental concerns by issuing educational campaigns to raise awareness about the features and benefits of AFVs [31,32,65]. In this respect, consumers seem to react more to emission information (eco-labelling) at the vehicle level than at the class level [60]. In addition, tax incentives (e.g., surcharge of dirtier fuels, differentiation of vehicle taxes based on fuel economy or CO₂ emissions), subsidies or private privileges (e.g., free parking) should make these vehicles more financially competitive as compared to conventionally fuelled vehicles [32,65]. Finally, the availability of a refuelling or recharging network could be ensured by the deployment of public charging stations, which is likely to be facilitated by the involvement and cooperation between all major stakeholders [31].

3.4 Other studies

A fundamentally different approach is symbolism, which does not focus on monetary costs and functional attributes to predict the adoption of AFVs, but on the symbolic meanings associated with them. Studies of symbolism either rely on conceptual frameworks from psychology (see [57,82]) or on ethnographic interviews which originate from anthropology (i.e., semiotics) (see [45,46]). The former studies used social-scientific research techniques to illustrate that the attractiveness of car use not only depends on instrumental-reasoned factors (e.g., travel costs, safety), but also on symbolic-affective motivations (e.g., status and social comparison, feelings of self-expression, feelings of sensation). The latter studies by Heffner et al. [45,46] assume that vehicles are important carriers of symbolic meanings that are used to maintain (product as self-expression) and create (product as self-creation) self-identity. By selecting a particular vehicle, people communicate their interests, beliefs, values and social status.

Semiotic theory often uses qualitative surveys as they allow participants to use their own terminology and value frameworks. In addition, it might overcome some of the challenges associated with the examination of symbolic meanings, such as the tendency to understate the impact of symbolic meanings in vehicle purchases [45,46]. On the other hand, this approach relies on the existence of AFVs on the market and associated symbolic meanings, which take time to appear and to communicate [75].

The reviewed studies, summarised in Table 6, mostly relied on semiotic theory to unveil the symbolic meanings associated to AFVs in California (US). They all agree on the fact that households are not purchasing AFVs for their functional or economic benefits, but to gain access to symbols that are used to define and express who they are.

Table 6 Reviewed other studies

Symbolism is found to be particularly strong in vehicles that use new types of technologies. They were important to early buyers of EVs in Norway [36] and HEVs in the US [45,46]. Heffner et al. [45] used ethnographic interviews with 25 early HEV buyers to explore how widely recognised social meanings (denotations) are connected to more personal meanings (connotations) and how they affect vehicle purchase. They revealed that households buy HEVs for the meanings they symbolise (such as “environmental preservation”, “financial responsibility”, “independence from oil producers”, “embracing new technology” and “opposition to war”) as well as the connotations linked to these ideas that are relevant to self-identity (such as “concern about others”, “intelligence”, “independence”, “uniqueness”, “ethics”, etc.). While denotations are generally socially-shared, connotations vary from person to person. For example, two households may view their HEV as a symbol for “preserving the environment”, but one household may emphasise the “ethics” connotation, whereas for another household their “concern about others” is an important value to communicate to society [45,88].

Heffner et al. [46] recommend that, just as early buyers of HEVs looked for meanings that were unavailable in other types of vehicles; early buyers of HFCVs will also look for new symbolic meanings in their vehicles that are not offered by competing alternatives. In this respect, HFCVs should improve on existing symbolic meanings (e.g., by providing potential buyers a more authentic access to the ideas of environmental preservation or advanced technology). In addition, they should offer entirely new symbolic meanings as well such as “home refuelling”, which can refer to aspects of independency. Another possibility is to explore the idea of “extended personal territory”, as HFCVs have the potential to produce clean electrical power for purposes other than propulsion. As new meanings will continue to emerge, understanding the meanings, as well as their construction and communication is essential to promote the AFV market.

4 Conclusions and recommendations

4.1 Conceptual framework and research methodologies of reviewed studies

This paper reviewed 53 publications according to the applied conceptual framework and research methodology. Overall, the amount of articles dealing with consumer preferences and attitudes towards AFVs has grown considerably over time. Research from the 80s and 90s was mainly carried out in California and applied preference valuation techniques and experimental designs to elicit consumer preferences for EVs. Recent studies, mainly executed in Europe and (North) America, give more emphasis to biofuels, hydrogen, (P)HEVs and HFCVs and also apply attitudinal surveys and (symbolic) qualitative surveys as reaction to the traditional rational-actor approaches. Early studies from the US often focused on EVs, which possess vehicle attributes that are unfamiliar to consumers. As a result, performance characteristics often came out as the critical acceptance factors. In recent studies from the EU, focusing on evolutionary technologies such as HEV or hydrogen, price characteristics play a more important role as the consumers are much more familiar with the performance attributes.

The predominant method used in measuring the consumer preferences for AFVs is CM, which principal aim is to unveil the different critical factors for the adoption of AFVs. A common criticism of CM is that they might not capture the complexity of a consumer purchase decision as it (1) only presents a small (pre-defined) selection of vehicle attributes in order to reduce the cognitive burden of the respondent and to allow proper measurement—leaving people no possibility to frame the perceptions by themselves and (2) assumes that respondents have preferences for attributes (such as driving range, home recharging) that are unfamiliar and unknown to them. A common criticism of SP surveys which also applies to (quantitative) attitudinal surveys is that the potential demand for green and progressive technologies might be overstated as a result of social desirable answers. In this respect, qualitative surveys (such as in symbolic studies and attitudinal surveys) and experimental based approaches (trials, travel diaries, etc.) increase familiarity and experience with the alternative technologies and offer more opportunities to deal with the socio-cultural contexts in which values, beliefs, perceptions and attitudes are rooted. On the other hand, these studies often contain small samples which are unlikely to be representative for wider populations.

The technological focus of experimental studies and symbolic studies is merely on EVs, PHEVs and HFCVs. These technologies not only face driving range and infrastructure challenges, but also possess new vehicle qualities such as silent driving, home recharging, etc. Experimental and symbolic studies mainly envision the early buyers segment and examine whether these new vehicle characteristics can offset the limitations (experimental studies) or even symbolise new meanings that can be communicated to society (symbolic studies). Attitudinal studies are rather performed to uncover the consumer attitudes for biofuels and hydrogen whereas consumer preference studies often deal with a variety of technologies. A potential gap in most of the reviewed studies is that they focus solely on the preferences for one technology [75]. Ideally, conventionally fuelled vehicles and other competing clean vehicle technologies should be incorporated in the study design to provide a better reflection of the range of alternatives that are available in the market and to improve realism.

4.2 Key results of reviewed studies

Overall, the key finding from the reviewed studies is that there exists a strong environmental concern, and positive attitudes towards AFVs, but that the environmental benefits are of little importance in the car purchase decision.

Attitudinal studies refer to this phenomenon as the attitude-action gap, as positive environmental attitudes do not translate into ecological behaviour. The revised literature revealed that attitudes of people are not only determined by environmental considerations, but also by a complex trade-off involving the perceived costs and benefits of the various alternatives. Moreover, limited knowledge levels currently prevent to build up awareness of AFVs, which is the key for their adoption.

Most experimental studies shared the opinion that a short-term exposure to AFVs improves the respondents’ overall impressions, especially with respect to their environmental benefits. But once experience with AFVs is gained, environmental benefits become of minor importance as other vehicle features (e.g., driving range) will enter the decision set. Nevertheless, some studies stipulate that acquired experience with AFVs attract so-called “hybrid households”, because of their new qualities (e.g., quite ride, low running costs, home recharging) which can more than offset the disutility of a reduced range. Again, these studies also recognise that environmental concern is not an important attribute in the car purchase decision, even for early AFV buyers.

The reviewed preference valuation studies unveiled that environmental benefits are of minor importance for the adoption of AFVs, which is principally driven by price characteristics, performance and convenience attributes. Additionally, the revised CV studies highlighted that the WTP for AFVs is positively influenced by socio-economic (e.g., income) and psychological characteristics (e.g., environmental concern), but that ultimately the WTP is still driven by expectations of personal financial savings. Recent studies also reveal that the degree of market penetration of AFVs might exert a strong influence on consumer preferences (i.e., neighbour effect), given equal monetary costs. However, these dynamics seem to depend on the type of technology such that preferences will be stronger for evolutionary technologies (e.g., HEV) than for disruptive technologies (e.g., HFCVs, EVs) as the latter possess vehicle attributes that are unfamiliar to consumers and require technical infrastructure.

Lastly, a different approach is the acknowledgment of symbolism as a central aspect of vehicle ownership. All revised studies agree on the fact that households do not purchase AFVs based on rational factors, such as functional or economic benefits, but to gain access to a variety of denotations and associated connotations behind it. In this respect, people might purchase an AFV as it symbolises “environmental preservation” and refers to a range of connotations such as “ethics”, “intelligence”, “awareness” or “concern about others”.

4.3 Policy recommendations

The adoption of AFVs is likely to be limited without significant governmental incentives and regulations.

Given the low awareness of AFVs found in the reviewed attitudinal studies, information provision is a prerequisite for changing environmental behaviour. It should be diversified according to the heterogeneous target audience (e.g., along their interests, knowledge, attitudes, socio-demographics, etc.) and should especially focus on the opportunities and possible solutions such as the range of actions that can be taken within car purchase to reduce energy problems. As AFVs are often associated with reduced performance and comfort, information about their performance potential might even attract people that are uninterested in environmental issues.

Besides educational campaigns to raise awareness about the features of AFVs, experimental studies and preference valuation techniques also highlight the need for pricing measures (e.g., differentiation of taxation based on fuel consumption or CO₂ emissions, subsidies, etc.), supply-sided measures (e.g., recharging, refuelling network) and large-scale demonstrations to ensure the financial attractiveness, availability and reliability of AFVs.

According to the symbolic studies, the market success of AFVs will depend on the existing and new symbolic meanings that are attached to these vehicles. In case of EVs, PHEVs and HFCVs, the challenge is thus to exploit new symbolic meanings that were not previously available in other vehicle types. However, if one wants to offer potential buyers stronger, more authentic access to these symbolic meanings such as “environmental preservation”, “oil independence” or “financial acumen”, a broad consensus about their environmentally friendly aspects or financial attractiveness should exist. Any confusion about these aspects (e.g., about the sustainability of the fuel on a well-to-wheel basis) could strip these potential symbolic meanings from AFVs. In this respect, common information tools that provide factual information on the potential environmental and financial benefits of AFVs are required in order to distinguish them from conventionally fuelled vehicles.