Sys tem atic eval u a tions of con cept de signs in volve con sid er ing a range of cri te ria. In ter ac tion with in dus try sup ports the view that re li abil ity is a ma jor cri te rion among those con sid ered in prod uct de sign. Al though there are few meth ods to pre dict re li abil ity in the ini tial phases of de sign, most of them are only ap pli ca ble to adap tive de signs. In this pa per, we in tro duce the con cept of rel a tive re li abil ity risk as sess ment for orig i nal de signs, where in for ma tion avail abil ity is less, to cal cu late re li abil ity. We con sider the func tion struc tures of the prod uct un der con sid er ation and ap ply the an a lytic hi er ar chy pro cess us ing ver bal as sess ments for rel a tive mea sure ments. The weight as sign ing tech nique used is the en tropy method. a fi nal value of R 3 I (Rel a tive Re li abil ity Risk In dex) is cal cu lated and the idea of con cept func tion al ity graphs is pre sented. This method is ap plied on the ex am ple of seat sus pen sions for an off high way ve hi cle and the re sults are dis cussed. The find ings help to sort out the con cepts that are rel a tively strong in terms of re li abil ity.

The Conceptual design phase generates various design concepts and these are then evaluated in order to identify the 'Best’ concept. Identifying the Best concept is important because much of the product life cycle cost is decided in this phase. Various evaluation techniques are performed so as to aid decision-making. Different criteria are weighted against concepts for the comparison. This paper describes the research being carried out at the University of Glasgow on design evaluation. It presents the Application of fuzzy logic for design evaluation and proposes an integrated decision-making model for design evaluation. This is a part of research project that aims at developing a computer tool for evaluation process to aid decision-making.

I (Relative Reliability Risk Index) is calculated and the idea of concept functionality graphs is presented.  This method is applied on the example of seat suspensions for an off highway vehicle and the results are discussed. The findings help to sort out the concepts that are relatively strong in terms of reliability.