How does the optimal mobility app look like? – An investigation of usage expectations, usage barriers and usability aspects

The Stuttgarter Straßenbahnen AG (SSB) has been providing mobility services in public transport in Stuttgart and the surrounding area for over 150 years. The goal of the SSB is to fulfill its tasks as customer-friendly as possible and thus to gain additional passengers – especially with a view to air pollution control. As an important step to increase the attractiveness of public transport in Stuttgart, the so-called polygo app is now to be developed. The polygo app is intended to become a user-friendly information and booking platform which offers access to multi-modal mobility offers in Stuttgart and the region. Mobility services offered by SSB FLEX, as well as bicycle rental, carsharing and e-scooter providers are to be integrated in the app.

Source: SSB AG

In their research, a team of six business psychology students from the Stuttgart University of Applied Science (HFT Stuttgart) identified usage expectations, potential usage barriers and usability improvements in order to support the SSB to achieve their goal of making the polygo app one of the top 3 mobility apps in Stuttgart. For this purpose, the team followed a multi-method approach and conducted three studies: qualitative interviews, a quantitative survey, and a usability test.

Study 1 and Study 2:

In the first study, 18 qualitative interviews were conducted with non-users, occasional users and regular users of public transport that were either students, trainees, or working people between 20 and 54 years. The goal was to find out what users expect from an optimally designed mobility app and what may be potential usage barriers. The next study was a quantitative survey with a 111 participants that lived within the area that is served by the mobility provider. The sample consisted of university students, working people, trainees, and high school students. Overall, 67% identified as female, 31% as male and 2% as non-binary. The aim of the survey was to gain a broader insight into the importance of certain features and exclusion criteria identified in the first study.
Nearly all participants of the qualitative and quantitative study who were either regular or occasional users have already downloaded a mobility app. Surprisingly, this has also been true for most of the non-users of public transport services. A big share of these non-users had downloaded the Deutsche Bahn app with the intention to use it for cross-regional connections.

Usage expectations

The qualitative interviews revealed that quick and simple processes, a good overview, and the possibility of personalization, for example in the form of saving routes as favorites, are important success factors for a mobility app. The most important overview-granting functions were the display of the fastest route as well as of delays and cancellations and the possibility to search for a concrete address instead of having to type in the name of the station.
Further, interview participants stated that they would only exchange their currently used mobility app when the polygo app offered new and more attractive functions. Suggestions for attractive functions made by the interviewees, such as the possibility to rebook and reverse tickets directly in the app and the possibility to use the app without an internet connection were also rated positively in the quantitative survey. The BestPreis function which was developed by SSB was perceived very positively by the participants of both, the qualitative and the quantitative, study. This function enables the users to save money when using public transport: Before each ride, a ticket is booked. With the first booking of a ticket, the period under observation starts. In this period, all booked tickets are gathered and saved. At the end of the period under observation, the cheapest ticket combination is calculated, and the respective sum debited.
For some participants, an innovative mobility app should also consider future development opportunities such as the possibility to book a car via the app which then drives to your home autonomously to pick you up.

Usage barriers

Examples of no-go’s mentioned by a large share of the participants are the display of incorrect connections, costs for downloading the app and dubious payment methods. Apart from that, non-users stated independence and comfort as reasons for not using public transport and associated apps.

Study 3:

In a third step, the usability of the app was tested with a sample of 12 participants who used the comparable competitor app “WienMobil”. This app was chosen for the usability test because the future polygo app is to be designed by the same provider and will offer similar functions and features. The aim was to reveal potential usability problems and to generate suggestions for improvements. The basis of the procedure in this test was the well-established usability test method of „thinking aloud“. The usability test consisted of a briefing, a test task, a post-session interview and a subsequent questionnaire. Five different tasks were set, such as e.g. the planning of a route, enabling the display of CO2 emissions for all suggested routes, or registering for a mobility service.

Usability improvements

Overall, the usability test showed great results. In the use case of planning a route, participants immediately recognized where to type in the start and destination. Moreover, they valued the color-coded display of connections in the app, as well as the auto-complete function when typing in destinations. The app menu is perceived as well-structured and the registration process for mobility partners is clear.
Participants also expressed ideas that could further improve the usability, such as the display of favorite routes on a map or the option to sort mobility service partners by different criteria.
As for improvements, the test revealed some minor, major, and critical issues when using the app. The identification of favorized routes and the issue, that the ticket button did not appear in every view of the app posed minor problems. Moreover, participants were unable to locate the function that sorts the suggested routes by CO2 emissions which represented a major issue. Therefore, participants wished that CO2 emissions for suggested routes are displayed by default. Finally, the usability test revealed two critical issues. In one view, the field for entering the start and destination of the trip were interchanged, making it impossible for participants to complete the task. Besides that, the procedure for favorizing routes was not intuitive.


The present research investigated usage expectations, usage barriers and usability aspects of a mobility app. The findings show that users expect an optimal mobility app to be simple to use and to offer options for personalization to make the use even more convenient. In order to encourage users of currently available mobility apps to switch to polygo, added value has to be provided to customers. This can be in the form of advanced functions, such as rebooking and reversing purchased tickets automatically within the app. To target non-users of mobility apps, one could consider including cross-regional connections. However, it has to be assessed, whether this function would encourage non-users to use public transport more often, since some stated motives for non-usage to which an app cannot react to, such as independence and comfort. Regarding the usability of the polygo app, the search for mobility partners should be improved through e.g. including filters in order to facilitate more efficient navigation on the app. Summing up, the optimal mobility app should be easy and smooth to navigate, while offering options for customization and advanced functions, to motivate customers to use it and encourage a sustainable way of transportation.


What’s your take on this? How would your perfect mobility app look like? We’re happy to hear about your ideas.