# A Comparative Study of the Availability of Electric Buses in the Public Transport System
## 1 Introduction
The study covered seven brands and types of buses and six categories of downtime. Technical availability was shown to be strongly correlated with outage categories and loosely correlated with bus age. Reference [16] presents the influence of selected factors of technical availability of public transport buses using the examples of Solaris and Mercedes-Benz buses in the Municipal Transport Company. A study of changes in technical availability was carried out with a division into two periods of use: warranty and post-warranty. A one-factor analysis of variance was used to test the significance of differences in mean availability values depending on the bus brand and depending on the periods of use. It was shown that in the warranty period, the technical availability of buses of both brands is comparable, while in the post-warranty period, it is significantly different. Reference [17] describes a mathematical model of the operation process of vehicles supplying fuel to aircraft prior to flight. The phase space of the investigated process was mapped using a seven-state vehicle operation model. Markov chains and processes were used to calculate the technical readiness index, K\({}_{\rm G}\)(t). Optional methods for determining the vehicle's technical readiness index based on the total operating time of the facility in each state are presented. Reference [18] proposes an author's method for assessing helicopter availability using Markov processes. An assessment of the availability of Mi8 helicopters equipped at the Transport Aviation Base is presented. Based on the analysis of the exploitation process, nine exploitation states are distinguished, for which boundary probabilities are calculated in discrete and continuous time. In the field of public transport, there has been a rapid increase in the number of electric vehicles in recent years. This trend is expected to continue into the future. The use of electric propulsion, especially in public transport, is primarily aimed at reducing local emissions, i.e., dust and gases that are harmful to human health, as well as carbon dioxide, which contributes to the global warming process [20; 21]. The characteristics of the size of the urban bus fleet in Poland in 2023, including the share of electric vehicles, are shown in Figure 1.  
Currently, in Poland, the share of electric buses in the total number of public transport buses is about 7%. The leading manufacturer of electric buses in the country is Solaris [24]. In view of the dynamic development of electromobility programmes, there is a need to assess new electric vehicles being launched on the market from environmental, economic, and technical points of view. In the literature, examples of assessing the operational maintenance of electric buses are quite few and methodologically diverse [25; 26]. Lublin is a city with a very long tradition of using electric vehicles in public transport. It is one of three cities in Poland, apart from Gdynia and Tychy, where trolleybuses are used. What distinguishes Lublin trolleybuses from other electric vehicles used in Poland and Europe is the fact that all of them are equipped with autonomous energy sources. These are serial hybrid systems and lithium-ion batteries of various types, mainly NMC, LFP, and LTO batteries. The experience gained during the operation and servicing of trolleybuses by Municipal Transport Company Lublin (MTCL) resulted in the creation of a system of electric buses 'tailor-made' for the city of Lublin. These buses have a relatively short range, around 70 km. Thanks to the knowledge, years of experience and appropriate use of battery technologies, together with appropriate charging infrastructure, these buses can perform transport tasks without downtime needed for charging. Properly designed infrastructure  
Figure 1: Public transport fleet by province in 2023; authors’ own elaboration based on [22; 23]. for electric vehicles allows for charging times to be minimised and for the vehicles to be used similarly to diesel vehicles [27].