Background: Physical inactivity is globally recognized as a major risk factor for morbidity, particularly the incidence of non-communicable diseases, and mortality. Engaging in active transportation (AT) is a viable approach toward increasing physical activity (PA) on a daily basis. Mobile (mHealth) interventions enable promoting AT to a larger population. The Smart City Active Mobile Phone Intervention (SCAMPI) study is a randomized controlled trial designed to evaluate a smartphone application (app)’s ability to motivate participants to increase their PA by engaging in AT.

Objective: This qualitative study examines the acceptance and usability of the SCAMPI app from the participants’ perspectives.

Methods: Seventeen residents of Stockholm county (13 women; age range 25-61 years), who had completed the three-month, app-based behavioral change program in the SCAMPI randomized controlled trial during 2018 agreed to participate in a semi-structured telephone-based interview. These 17 participants were well representative of the whole intervention group (n = 127) in terms of baseline characteristics such as age, sex, and area of residence. The interviews were audio-recorded, transcribed verbatim, and analyzed using inductive qualitative content analysis.

Results: The content analysis revealed two themes and four subcategories. The first theme “Main motivators: monitoring and messages” highlighted that monitoring AT and being able to set weekly goals using the app were the primary motivators reported among study participants. The second theme “Acceptable but modifiable” reflects that the app was well accepted and effectively encouraged many participants to use more AT. Nevertheless, there were functions in the app that require modification. For example, while the automated travel tracking feature was appreciated, participants found it time-consuming and unreliable at times.

Conclusions: This study contributes novel insight into healthy adults’ experiences of using a mobile app to promote the use of AT. The results showed that the app was well-accepted and that self-monitoring and goal setting were the main motivators to engage in more AT. The automated tracking of AT was appreciated; however, it was also reported to be energy- and time-consuming when it failed to work. Thus, this feature should be improved going forward.