## 5 Conclusions  
It is well known that stop dwell time is affected by various influential parameters such as the number of passengers, the type and characteristics of tram vehicles, the tram stop platform characteristics, and the position in the traffic network. However, local surveys and studies regarding tram stop dwell time are essential for the creation of stable, feasible, robust, and resilient timetables for PT. The presented research is the first study conducted on the tram system in the City of Zagreb, and it deals with the analysis of parameters that influence tram stop dwell time. Therefore, the main objectives of this research were to develop and validate a methodology for tram stop field data collection and laboratory processing, to determine locally representative tram stop dwell time values for three tram vehicle types (TMK301, TMK2100, and TMK2200) serving island platforms in Zagreb, and to analyze the impact of rolling stock heterogeneity on tram stop dwell time. The presented analysis shows that it is possible to collect and analyze detailed and high-quality data on the type of tram vehicle, passenger exchange (boarding and alighting volumes through specific doors), and stop dwell time by video recordings of the operations on platforms. Due to the relatively small amount of data collected for tram vehicles TMK2100 and TMK2200 compared to the amount of data collected for tram vehicle type TMK301, the data analysis was performed to identify the trend between the number of passengers, passenger flow type, and stop dwell time for each tram type, rather than to quantify the relationships and interactions between the observed variables. For the investigation, it was assumed that the trend was linear, and the trend analysis was undertaken within a formal regression analysis. The initial statistical analysis results showed that for volumes of up to 10 passengers per tram (150 passengers per hour), the average time taken for passenger exchange was around 13 s. Furthermore, the tram vehicle type influenced stop dwell time in the following manner. The height of the floor, the number of doors per tram, and the door width did not influence the process of passenger exchange. The tram stop dwell time was primarily affected by the time needed for doors to open and close. For volumes of up to 20 passengers per tram, passengers mostly boarded through the doors nearest to the shelter and stop sign. In such conditions, the trend analysis showed that dwell time was mostly affected by the tram door opening mechanism and opening/closing time. As the passenger volumes became higher, the distribution of both boarding and alighting passengers became more uniform along the island platform and through the vehicle doors. Therefore, the number of doors per vehicle became more significant, i.e., trans with a smaller number of faster opening/closing doors had the same dwell time as trans with a greater number of slower doors. The results provided the following guidelines for further research. For detailed regression analysis and the determination of specific impacts of tram vehicle characteristics on stop dwell time, it was necessary to supplement the database created for the presented research with data obtained for the remaining two types of tram vehicles in operation on the Zagreb tram network. Therefore, it will be necessary to expand the research locations to stops inside the city center as well as to those farther from it. Further research should also focus on determining closer relations between the type of tram vehicle, passenger flow type, and passenger flow time through the busiest tram doors. The creation of a regression model regarding this expanded data set will enable a detailed analysis of the joint influence of multiple factors on tram stop dwell time (tram type, platform location and design, and passenger exchange volumes and types) and exploration of their interactional mechanism. Conceptualization, M.A. and I.M. ; methodology, M.A. ; validation, I.M. ; formal analysis, I.M. ; investigation, I.M.