CONDITIONS RELATED TO THE ROOF STRUCTURE STRENGTH OF BUSES POWERED BY NATURAL GAS AND FUEL CELLS

Modern public transport is increasingly turning to cleaner energy solutions such as compressed natural gas (CNG) or biomethane and hydrogen fuel cells. These technologies help reduce air pollution and greenhouse gas emissions, making buses more sustainable compared to traditional diesel vehicles. However, the use of alternative fuels also creates new engineering challenges, especially in relation to vehicle safety and structural design. One important issue is the strength of the bus roof. In many CNG and fuel cell buses, heavy storage tanks or fuel cell systems are installed on the roof. This additional load changes how forces are distributed across the vehicle and may influence how the structure behaves during accidents, such as rollovers. Ensuring that the roof can safely carry these components while still protecting passengers is therefore a critical part of bus design. This paper examines the conditions that affect roof structure strength in buses powered by CNG. It focuses on how roof-mounted components influence mechanical performance, safety compliance, and overall reliability. The regulations UN ECE 110R and UN ECE 115R more closely define the technical requirements for the installation and homologation of natural gas devices and equipment. The aim of presented researches is to contribute to the development of safer and more efficient bus designs that support sustainable public transport. The presented calculation methods are also applicable to fuel cell and battery electric buses.