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The worldwide COVID-19 pandemic revealed societal challenges, with passenger transport rapidly experiencing the impacts of the virus and the evolution of the concept of safety in transport. Evaluating the likelihood of viral transmission within transportation systems may be a substantial challenge, considering the complex processes that influence the incidence of random transmission events. This paper introduces a method for determining the probability of pathogen transmission in public transport, focusing on the SARS-CoV-2 virus. The study draws on scenarios from the first and second waves of the COVID-19 pandemic in Poland, a period that was devastatingly marked by the lack of available vaccines. This study aims to add value to the scientific community by offering an estimation of the likelihood of SARS-CoV-2 transmission in public transport and a preliminary risk assessment for COVID-19 infection, considering the number of active, non-isolated COVID-19 cases in the Polish population. The potential of this approach was demonstrated through a comparison between two different categories of passenger transport in a city bus. Based on the presented case study and the calculated probability of pathogen transmission, it is estimated that the probability of SARS-CoV-2 infection during the second wave of the COVID-19 pandemic in Poland through the use of public transport was approximately 0.05%. Probability estimations based on elementary events, which can vary depending on the service category (for instance, the form of ticket purchase, availability of seating or standing places, or ticket inspection), can reveal even the smallest differences in the total likelihood of pathogen transmission. However, these minute individual variations significantly impact the total metrics calculated for daily users of public transport. For effective monitoring of potential epidemic threats and for designing suitable interventions and restrictions to lower the risk of future pandemics, it may be necessary to understand the role that transportation systems, particularly public transport systems, play in the spread of pathogens.

This article presents results of tests of the effect exerted by technical condition of shock absorbers on the braking efficiency of an automotive vehicle. The tests were conducted using Fiat Seicento featuring front shock absorbers which enabled shock-absorbing fluid-level adjustment. The tests comprised measurements conducted on the shock absorbers in four states, i.e. the nominal state with the fluid level at 100%, with shock-absorbing fluid levels of 25%, 50% and 75% as well as with the fluid tank completely empty (0%). Road tests of braking efficiency were conducted on cobbled pavement by means of a decelerometer.

Vibration phenomena occurring in vehicles are very relevant for safety and comfort. Passenger car must be considered as a multi-technical system in which there are non-linear phenomena. Therefore, vibrations occurring in vehicles should be analyzed in many points of car structure and relate them to other criteria analysis. The paper presents examples of the results of vibration and their distribution at selected points during laboratory research and road tests.

The results of the examination of a vehicle suspension system in the plate position are presented in the paper. The model vehicle is a Fiat Seicento with front independent suspension, McPherson type, with the steering system and with the semi-trailing arm in the rear suspension. Identification of the model was made by comparing the simulation results with the results from the test stand. A multibody model of the vehicle will be used in studies of the impact of shock absorber technical conditions on the dynamics of automotive vehicles.

This paper presents results of the modern vehicle shock absorbers’ researches on indicator test stand. On this stand can be determined the diagrams of force versus displacement and force versus velocity. These diagrams can be determined for changeable strokes and constant velocities or the opposite way round. In researches the modern hydraulic twin-tube vehicle shock absorber was modificated and the changes of oil volume were possible. There was determined the influence of oil volume changes on force versus displacement and force versus velocity diagrams. On the basis of force versus velocity diagrams, the dumping characteristics were determined (value of force for maximum velocity on this diagram). The influence of oil volume changes on dumping characteristics was determined too. The results of this investigation can be used in simulation researches of vehicle suspension dynamic.

The paper presents results of vibro-acoustic signal analysis (acceleration of the unsprung mass of passenger’s car suspension actuated to vibration by harmonic, kinematic vibration). The range of research has included front shock absorber for Fiat Seicento with simulated fault (oil leak). Force process consisted of three phases: increase of frequency, vibration with constant frequency (above 21 Hz) and decreases of frequency.For the analysis process Short Time Fourier Transform method was used with superposition of rectangles window and with zero complement method. On STFT spectrum resonance frequency of unsprung mass was identified. The estimator was the means of maximum acceleration amplitude peak in frequency band round resonance frequency. The result of investigation was presented on diagrams with changeable value of estimator for different technical conditions of shock absorber (with different volume of oil inside the shock absorber)

The paper presents possibilities of applying linear decimation procedure in frequency analysis of non-stationary signals. It shows the results of analytical experiments conducted with vibration signals registered during examination of car suspension which was activated to vibration on harmonic stand research. Working cycles identification algorithm was helpful to make LDP of working cycles parts of a signal. Signals spectrum results confirm amplitude selectivity for typical frequency ofresearching dynamic system.