## 2 Materials and Methods
### Survey Design  
The present paper utilizes data from two questionnaires. The first questionnaire applied to the users of the bike-sharing system in the city of Thessaloniki, while the second was applied to other residents of the city (potential users of the bike-sharing system). The development of the two questionnaires was inspired to a large extent from mobile apps that are used by bike-sharing systems, which are mainly located in European countries. Both questionnaires include the following sections:  
* Section I: It is exactly the same in the two questionnaires. The questions that it contains concern the following: (a) gender, (b) age, (c) address, (d) occupation, (e) level of education, (f) household income, (g) exercise frequency, (h) private car ownership, (i) bicycle ownership.
* Section II: It is also exactly the same in the two questionnaires. In this section the respondents are asked to describe their most usual trip within the day (origin, destination, purpose, hour, transport mode), to reveal the frequency of using a private car or bicycle, to describe their most usual trip with bicycle (origin, destination, purpose, hour, percentage of the journey carried out through bicycle lanes), and to state the conditions that are needed to be met for using a bicycle more frequently for commuting.  
Figure 1: The network of bicycle lanes and the stations of the ThessBike system in the city of Thessaloniki.  
* Section III: The differences between the two questionnaires are identified in this section. Existing users of the ThessBike system were called to complement: (a) an area that they would like to be served by a bike-sharing station, (b) the most usual purpose of their trip when using the ThessBike system, (c) a grade for five different attributes (number and location of stations, quality of bicycles, rental process, rental cost, provided information) of the ThessBike system, (d) a grade for the usefulness of thirteen different services that a bike-sharing app can provide and (e) if a state-of-the-art app, which will provide all the thirteen services, would guide them to use the ThessBike system more often. On the other hand, potential users were asked to fill in: (a) an area that they would like to be served by a bike-sharing station, (b) a grade about the effect that specific factors have in their decision not to use the system, (c) a grade for the usefulness of thirteen different services that a bike-sharing app can provide and (d) if an app, that will provide all the thirteen services, would guide them to register to the ThessBike system. It should be mentioned that for the evaluation of the ThessBike attributes, the usefulness of the app services and the effect of the factors in not using the system, a five-point Likert scale was used [24].  
In the first step, a pilot survey was conducted, which resulted in small rephrasing in specific questions, in order to eliminate possible misunderstandings. The final versions of the two questionnaires were developed in electronic format and the link for completing them was shared in local websites, social media, and brochures that they were distributed during events. Additionally to the distribution of the link, questionnaires in printed form were also completed, mainly at the ThessBike stations, in an attempt to gather more data from existing users. The survey was conducted between 30 October 2018 and 20 November 2018. A total of 332 questionnaires were completed, 126 by existing users and 206 by potential users. Despite the fact that the main issue in web surveys is the absence of an interviewer and thus the inability to provide the appropriate clarifications to the respondents, the questionnaires were designed in an easy to follow way in order to avoid misunderstandings.