The mechanical engineering problems today become more and more complex particularly in the area of new product development. Mechanical product design is usually performed simply taking into consideration system functions and structures, while users’ behaviours in terms of using the system are generally not fully considered enough early in the design phase. This paper covers the multi-trade engineering design, and deals with the development of a behavioural design approach to help designers to optimize the product performance from design phase through taking into account utilization conditions and requirements._