## 2 Driver/Passenger Acceptance  
### Definition of Driver/Passenger Acceptance  
Since acceptance is primarily influenced by individuals' emotional factors, it is crucial to discuss and define what acceptance means in this study. In a previous study, a statement on the purpose of investigating the acceptance is shown: 'Driver acceptance is the precondition that will permit new automotive technologies to achieve their forecasted benefit levels'; another statement addressing the need to determine whether drivers will accept and use the new technologies as intended is as follows: 'Driver acceptance measurement also provides a means to estimate drivers' interest in purchasing and using new technologies as a basis for estimating the safety benefit associated with its use [16]. Acceptance is seen as the link to usage in [6], and acceptance is explained as a predictor of the willingness to buy a system [17]. While many studies claim the importance of acceptance and assessing the acceptance of new technologies, there are many different ways of viewing acceptance. A statement on a problematic issue of the definition of acceptance is as follows: 'While everyone seems to know what acceptability is, and all agree that acceptability is important, there is no consistency across studies as to what acceptability is and how to measure it' [4].  
The definition of acceptance identified in the literature was classified into five categories in a recent literature review [3]. The word \"accept\" is simply used for the first category: for example, 'acceptance is the degree to which a law, measure or device is accepted' [18]. The second category is defined concerning the satisfaction of the needs and requirements of users. For example, 'basically the question of whether the system is good enough to satisfy all the needs and requirements of the users and other potential stake holders' [19]. The third category is described as \"the sum of all attitudes\". For example, 'Acceptance refers to what the objects or contents for which acceptance is measured are associated to; what do those objects or contents imply for the asked person' [8]. The fourth category is explained by \"the will to use the system\". For example, 'acceptance is the intention to adopt an application' [20]. The fifth category focuses on \"the actual use of the system\". For example, 'the demonstrable willingness within a user group to employ information technology for the task it is designed to support' [21].  
In this study, if acceptance is not defined well, it is not only possible to assess acceptance, but also to build an assessment tool for an automatic lane change system. In order to achieve a study on an objective method of the acceptance for an automatic lane change system, acceptance is defined and suggested considering the target system as follows in the following statement.  
\"Acceptance is the classification to which an individual intends to use the system in his/her driving if the system is incorporated.\"  
This suggested definition of acceptance has the advantage of focusing on the individual perspective, both regarding the subjective evaluation of the system and the advantages of using the system. This provides the potential to realize the expected effects of the system. This definition also provides an opening for assessing a system in development by addressing the intention to use the system if the system was available as potential acceptance.