## 1 Introduction
This multidisciplinary approach ensures that structural improvements translate into tangible operational benefits across a range of real-world scenarios. While structural performance under operational loads is critical, occupant safety during collision events remains equally important. The study [17] investigates head injury risk in bus frontal collisions, focusing on the influence of structural configuration. Finite element sledge test simulations were conducted using acceleration data to analyse how interior components and body layout affect dummy kinematics and Head Injury Criterion--HIC15, which was reduced by approximately 5.6%. This underscores the importance of internal design in mitigating occupant injury beyond external crashworthiness. The authors of [18] used FEA to compare the current EN10025 S355 JR-type battery carrier frame material with alternatives like aluminium 6061-T6, aluminium 7075-T6, and carbon fibre-reinforced PEEK (Polyether Ether Ketone), achieving weight reductions of 65.54% and 73.07% with aluminium 6061-T6 and carbon fibre-reinforced PEEK, respectively. [PERSON] et al. [19] investigated a battery electric bus energy consumption model for strategic purposes and proceeded with the validation of a proposed model structure with data from bus fleets in China and Norway. Such models are essential for optimising operational efficiency and supporting broader electrification strategies. [PERSON] et al. [20] evaluated the crash performance of a bus front structure during a frontal impact. A finite element model was simulated in ANSYS/Explicit Dynamics using two impact velocities to assess deformation and deceleration. Energy absorption was validated using the Lag rangian function. A lumped mass model in MATLAB/Simulink helped estimate design parameters, and a Genetic Algorithm was applied for multi-objective optimisation. Experimental tests on four samples confirmed the findings. Results showed that beyond the first crash zone, safety limits were exceeded. To improve crashworthiness, extending the front deformation zone is recommended. [PERSON] et al. [21] presented a numerical dynamic analysis of a multi-body bus. Optimisation of bus body frame structure for weight minimising with the constraint of natural frequency using an adaptive single-objective method is a topic of [22]. These studies collectively contribute to the growing body of knowledge aimed at improving bus safety, efficiency, and performance through advanced simulation and optimisation techniques. However, simulation-based advancements must be evaluated in the context of long-term structural performance and real-world ageing effects. [PERSON] et al. [23] examined the ageing of bus bodies on frame chassis, finding durability ranges from 5 to 11 years depending on factors like occupancy, road conditions, speed, and corrosion. Such real-world factors significantly influence the lifespan and safety of bus structures, underscoring the importance of material choice and design in extending operational life. A frame made of alloy steel with closed profiles lasts 1.5-1.8 times longer than a body frame with open sections, affecting the bus's safety. Traditional bus body frame optimisation focuses on part thickness, but the study [24] optimises the sectional shape of tube beams using mesh morphing technology. While these studies focus on durability and structural enhancement, crash performance remains a critical dimension in evaluating modern electric bus safety. [PERSON] et al. [25] investigated the frontal crash behaviour of a low-entry electric bus frame under NCAP-like conditions at 32 and 56 km/h, using LS-DYNA software simulations to assess deformation zones influenced by added battery mass. The results show reduced body deviations and a safer deceleration profile at lower speeds, supporting a recommendation to lower NCAP test speeds for city buses, highlighting greater passenger risk compared to UNECE R29 due to deeper structural deformations.