A comprehensive crashworthiness analysis in the design of coaches, specifically focusing on adapting the ECE R29 standard, was made. The external fiberglass composite panels of two coach models were tested for replacement with a state-of-the-art polymer (DCPD). The analysis was based on the finite element method, using the software Pamcrash®, which evaluates the energy absorption capacity of the models, comparing deformation, displacements, and material penetration values over time. The assessment of the driver's residual space, as specified by the ECE R29 standard, is also included in the analysis. The Lean Design for eXcellence (LeanDfX) methodology was used, which involves multiple domains of analysis including model optimization, manufacturing process, and eco-design. It employs an index on a 0%-100% scale, to compare different 'X' domains, such as energy absorption capacity and material intrusion. An Eco-Design X study is also conducted to assess the environmental impacts of the proposed solution compared to the original models. Quantification is carried out using the Simapro v9.2.0.2 software with the ReCiPe 2016 methodology. The modifications proposed to the coach models are shown to result in significant improvement in the structural behaviour of the vehicle for driver's physical integrity in frontal impact scenarios. The cross results of Design-for-Crashworthiness and Design-for-Eco-Design using the LeanDfX framework provide a new perspective to be integrated in the automotive industry. The use of a state-of-the-art polymer (DCPD) for the external panels, is expected to lead to a more crashworthy and environmentally friendly design for coaches, while ensuring passenger safety.