Two freight platform wagons connected together conventionally or in the form of so-called rigid connection were taken into account to investigate the influence of unsupported sleepers on climb flange derailment on transition curve. Presented results are related to the freight wagons equipped with two-axle Y25 standard bogies, entering at an acceptable speed in the transition curve of the track with the radius of 150 or 1,000 m. Three cases have been analyzed: only the inner rail, only the outer rail, or both rails had unsupported sleepers. Simulation models were prepared using the VI-Rail software and nonlinear wheel–rail contact model. The dynamic calculations showed that wheel flange climb derailment caused by unsupported sleepers will only occur if deflection of the rail or track on transition curve is deep enough. These tests allowed us to determine the relationship between the radius of curvature and the depth of the trough causing derailment of the wagons. Calculation results allowed us to answer also the questions whether the method of connection and the weight of freight wagons have a significant impact on the wheel flange climb derailment.

One of the most basic issues in fluid mechanics is the description of flow in closed flows; more precisely, the calculation of pressure drops and the description of the flow form. Therefore, in this paper, the numerical simulation of the flow through the elbow was presented. This case was used to comprehensively describe the most important phenomena that should be taken into account during closed flows. The elbow was chosen as one of the most frequently used fittings in practice. The simulation was made with ANSYS Fluent, with the use of the turbulent model k-ω, SIMPLE simulation method, and at Reynolds number $Re=500-100,000$. The minor and major pressure loss were presented and discussed in the paper. The minor loss coefficient at the high Reynolds number was equal to around 0.2, which is close to the value of 0.22 used in engineering calculations. The influence of the Reynolds number on the shift of the stream separation point in the elbow was described. The secondary flow in the elbow was observed and the vortex structure was discussed and shown with the use of the Q-criterion (Q iso surface for level 0.005). This analysis allowed us to better visualize and describe the complex flow structure observed in the investigated case.

This article examines differences between conventional manual measurements of tram operations and data extracted automatically using the REWIZOR program, based on the Yolo10s algorithm. The study addresses the broader question of how artificial intelligence can support analyses of passenger exchange processes in public transport and improve the efficiency of data collection. Measurements conducted in four Polish cities included tram types, stop times, and detailed boarding and alighting durations, while the REWIZOR software enabled automatic detection of stop times and passenger flows based on video recordings. The results show that, although both approaches yield consistent qualitative information regarding doors and passenger counts, significant quantitative discrepancies arise. These differences stem mainly from methodological inconsistencies and varying definitions of boarding, alighting, and stop times, as well as from software-related detection errors. The findings indicate that AI-based measurements require calibration against reference methods to allow reliable comparison with conventional datasets. As currently implemented, REWIZOR can be used effectively for internal analyses of passenger flows, if all compared data come from the same system. Further development—such as implementing simultaneous tracking of people and heads—may considerably improve accuracy and facilitate wider applicability in public transport studies.

The processes of boarding and disembarking passengers in public transport significantly affect the travel time between tram stops. As a part of sustainable urban development, it is necessary to implement new techniques to streamline traffic and promptly respond to the public transport passengers' demand for efficient movement around the city. The structural solutions used in tram and bus vestibule areas are constantly changing to speed up these processes. Understanding passenger behaviors is a necessary element in optimizing passenger flow between the stop and the rail vehicle, as well as within the vehicle itself. However, there is a lack of data that could be used to evaluate specific solutions. The article measured boarding and disembarking times from a Pesa 122NaB tram example operated in the city of Bydgoszcz, which has a population of approximately 340,500 residents. Due to the city's functioning specificity, the analysis of passenger flow in trams differs from that in metropolitan areas with over a million residents because tram journeys in cities of this size occur on longer routes than in metropolitan transport, which results from the lack of alternatives to tram transport. Most analyses are conducted within metropolitan transport, where the dynamics of passenger flow will be significantly different than in medium-sized cities. This study analyzed a specific case where the district served by the tram line under analysis – Fordon – is separated from the city, generating a greater number of long-distance journeys. The study recorded 106 boarding and 126 disembarking instances from the tram. The studies were preliminary as part of a development project for an AI platform enabling real-time passenger flow analysis. The article analyzes the frequency of passenger numbers occurrence. The average passenger flow time was approximated by a linear function R2 = 0.94. The time per person decreased with the number of passengers; it ranged from 1 to 1.5 seconds for 5 or more passengers. The presented data can be used for further comparative analysis of passenger flow processes, both for the proposed AI algorithm and for analytical purposes for rail vehicle manufacturers and municipal public transport operators.

Ventilation ducts are the basic element of any ventilation system. The paper presents three shapes of ventilation ducts used in industry and discusses them with particular emphasis on the possibility of using them in the con-struction of shelters. Circle ducts, rectangular ducts, and rectangular ducts with rounded corners. The flow and strength parameters of the indicated ducts were analyzed, and the advantages and disadvantages of individual so-lutions were presented. Based on the conducted analysis, knowledge gaps were identified.

Wear of the top layer of the raceway of rolling bearings is a common problem in bearing operation. Its wear has been realized for over 50 years, but due to the use of rolling bearings in many industrial machines and technology development, it is necessary to constantly update the knowledge on this subject. The article reviews articles on the fatigue and tribological problems of the exploitation transformation of rolling bearings in terms of the current development trends in this field.