summarize Usability Evaluation Methodology for Public Transport Mobile Ticketing Solutions following paragraph:

2.1 Usability

The International Organization for Standardization (ISO, 2018) defines usability as the extent to which a system, product or service can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use. According to Nielsens (1993) classical definition, usability regards all features and prospects of a system which can be interacted and it is habitually identified by five attributes: learnability of the system, efficiency of use, easiness to remember (memorability), ability to recover from errors and subjective satisfaction.

According to Geisen and Bergstrom (2017), the concept of usability arose from the discipline of Human Factors and has been around for centuries. With the rise of personal computers in the 1980s, the terms usability engineering and usability became more prominent due to the importance of conceiving more intuitive PCs.

Marcus (2005, p. 17) states, as reason to put effort and resources in usability, that it increases customer satisfaction and productivity, leads to customer trust and loyalty, and contributes to tangible cost savings and profitability.

Besides that, in the internet age, usability is a condition for survival. If users find it hard to understand how to use a system (e.g. a mobile application or a website), they simply do not use it, there are plenty of other options available for them to try. The user will not persist in a system when facing difficulties unless they really must do so, such as in the case of employees and companys intranet (Nielsen, 2012).

2.2 Usability evaluation techniques

After clarifying the abstract concept of usability, it is necessary to methodically approach it and define forms of precisely measuring and evaluating it in order to improve products and users better understand them.

When software started reaching a larger audience in the early 1980s, usability evaluation techniques became more popular and, since then, many types of them have emerged (Dumas and Fox, 2008). Yez et al. (2014) provided a wide and yet non-exhaustive classification of such techniques, as shown in Figure 1.

Over real systems or prototypes, as is the case of public transport mobile ticketing solutions, evaluations conducted by experts or involving users are preferred. Predictive evaluations are frequently employed with an academic focus on under development (Yez et al., 2014).

2.2.1 Heuristic Evaluation

Heuristic Evaluation (HE), sometimes called Expert Evaluation, is an evaluation performed by experts using a heuristic checklist (Rosenzweig, 2015). Heuristics are predetermined standard principles, often composed of broad rules of thumb (Gumussoy, 2016). A checklist can be designed to aid experts in identifying usability problems, but they shall be also encouraged to give further insights beyond the checklist (Khajouei et al., 2018).

Experts are called like that to differentiate them from regular users, and although they are required to have previous knowledge on usability, they do not necessarily have to be usability experts (Nielsen, 1994; Yez et al., 2014).

HE methods main goal is to identify problems associated with the design of user interfaces and its main benefits are being a fast and inexpensive technique that yields meaningful results (Tan et al., 2009; Gonzlez et al., 2009).

2.2.2 Usability tests

Usability tests are a form of evaluation in which users are asked to interact with a prototype and give feedback about their understanding of it and easiness to use. The goal is to collect data empirically to make the prototype match the users mental model (Rosenzweig, 2015). As a result, Usability tests can benefit both users and companies greatly, by making products easier to use and, hence, improving profitability (Rubin and Chisnell, 2008).

According to Rubin and Chisnell (2008), it is fundamental to plan beforehand to develop a Usability test. The key elements include, but are not limited to: a concrete purpose and problem statement; identification of a representative sample of users; selection of test environment; clear definition of how test sessions will be conducted; collection of data; and report of findings and recommendations

2.2.3 Development of field-specific usability heuristics and checklist

Usability researchers and practitioners have long criticized traditional heuristics because they might not evaluate specificities of particular types of systems and may be too generic or broad. Therefore, many authors have developed field-specific sets of usability heuristics and checklists in order to perform such evaluations more efficiently and achieve more valuable results (Quiones and Rusu, 2017; Mosqueira-Rey et al., 2018).

According to Quiones and Rusu (2017), no consistent methodology has been employed through the various articles regarding development of field-specific usability heuristics. Although some models have been used more than others for instance, Rusu et al.s (2011) and Van Greunen et al.s (2011) , most researchers use solely their vast field-related experience and usability knowledge to develop new sets of heuristics and checklists.

Kuparinen et al. (2013) have proposed a methodology for establishing new specific usability heuristics by using traditional heuristics and adapting them a particular field. Yez et al. (2014) go further by researching comprehensively traditional and field-specific heuristic checklists and best practice manuals, then adapting and merging subheuristics to homogenize the redaction and format, so that the final heuristic checklist covers the application thoroughly.

Hermawati and Lawson (2016) agree to that by indicating that traditional heuristics, such as Nielsens, can be applied to evaluate various types of user interfaces if they are adjusted accordingly. That is, Nielsens heuristics may address a large portion of usability problems in an application, but if they are not adjusted to the applications field, specific usability problems might be completely missed.