###### Abstract  
Although the past research results have provided many effective tools for evaluating public bus service quality, they still lack the concept of risk. This study assessed the quality risk for city bus service by constructing a quality risk assessment model that integrated [PERSON]'s model, IPA, and FMEA. The online questionnaire was distributed to commuters who use BMTA's bus service in Bangkok with 429 samples. This study analyzed the service quality attributes of bus services via [PERSON]'s model, an IPA, and an FMEA. For the results of [PERSON]'s model, this study identified nine one-dimensional and three attractive attributes. The results of the IPA showed that the safety of boarding and disembarking from the bus, the cleanliness of vehicles, and the punctuality of buses according to the schedule were the top three attributes that had a large gap between importance and satisfaction. According to the results of the FMEA, the safety of boarding and disembarking from the bus, the cleanliness of vehicles, and the punctuality of buses according to the schedule were the top three attributes that had a high service quality risk and considered a priority improvement. These attributes belonged to interaction with passengers, tangible service equipment, and operating management support dimensions. Therefore, the government should take action and improve service quality to make Bangkok commuters consider switching from driving cars to using a bus. Finally, this study provides practical improvement strategies for managers to improve passenger experiences and enhance the quality of bus services. bus service; service quality risk; [PERSON]'s model; importance-performance analysis; failure mode and effects analysis +
Footnote †: journal: Medical  
Kidbunjong [3] identified the issues and challenges confronting Bangkok's mass transit system development, and they showed that the quality of the mass transit system in Bangkok lags behind other major cities in the region. The rail project was developed as a stand-alone project with no connection to the bus system. The network connection between the public transportation system, the activity source, and the community is inefficient. Moreover, Bangkok residents spend a lot of time and travel expenses without being able to predict the time it takes to travel. The traffic area is mainly occupied by private cars. Bangkok is known for its severe traffic congestion and has a congestion level of 44%. This means that a 30 min trip in Bangkok will take 44% more time than it would under normal, uncongested conditions. Furthermore, a study reported that Bangkok commuters spend an additional 35 min per trip, resulting in an opportunity cost of THB 11 billion annually or THB 66 million daily [4]. This issue also led to a THB 6 billion increase in Thailand's fuel spending per year and forced many Bangkok commuters to reallocate their spending [5]. The government is making efforts to encourage residents to use public transportation instead of personal cars in order to reduce road congestion and address PM2.5 issues, which are primarily caused by cars. However, the coordination in addressing these issues is not as unified as it should be, and there are still flaws in the discipline of road users. All of these things are important factors causing more traffic problems. However, the service attributes are numerous and wide-ranging. Commuters are not only concerned about safety, speed, punctuality, and convenience, but also value the driver's service attitude, information provision, a friendly ride environment, etc. [6]. From a business operation perspective, in a fiercely competitive market, improving service quality to attract customers and make them loyal customers has become an important issue for many companies. However, when faced with limited resources, knowing how to formulate improvement strategies is an important issue.