# Performance-Based Ranking of Existing Road Bridges
###### Abstract
The basic approach of the performance assessment method presented in this paper is the weighted sum method, which is used to evaluate the individual bridge elements and their contribution to the overall performance of the bridge. When using the weighted sum method, it is recommended that the factor-based or age-based variable weighting method be considered to account for the weight distribution in the performance evaluation of bridge systems, as described in the work of [PERSON] et al. [19]. The success of management systems applied to bridges within a given road network exposed to various phenomena depends on the ability to maintain satisfactory performance of these bridges during their service life. On the other hand, the evaluation of bridge performance depends on its safety (e.g., load-bearing capacity), stability, functionality (e.g., traffic safety and free circulation), durability, serviceability, cost efficiency (e.g., maintenance costs, traffic closure costs), and environmental impact. An overview of current measurement approaches and methods, as well as the most critical aspects of bridge performance, is presented in the Federal Highway Administration's Long-Term Bridge Performance (LTBP) Program Report--Bridge Performance Primer [20; 21]. In addition, an overview of bridge performance measures in relation to bridge project objectives can be found in the University of Wisconsin project report [21; 22]. At the European level, the International Organization for Economic Co-Operation and Development conducted a survey of performance indicators for the roads sector, starting in 1995, and identified 15 performance indicators among those used by road administrations around the world [23]. Most of them are related to road-user satisfaction and asset management and can be considered as indicators of the socio-economic performance of a bridge. Later, other studies [24; 25; 26] were conducted to evaluate the performance of infrastructures and bridges using sustainability criteria that integrate environmental, economic, and social criteria over the life cycle. In addition, the COST Action C25 [27; 28] was carried out, aiming to promote a scientific understanding of life cycle engineering and to advance the science-based development of sustainable construction in Europe. The results are mainly construction-oriented, although some examples of LCA (life cycle assessment) of bridges can be found. The results of another COST Action 354 [29], dealing with performance indicators for road pavements, are a good example of a level-based approach, the development of combination methods, and weighting factors. It starts with the single performance indicator (_PI_), which refers to only one characteristic; through combined performance indicators (_CPI_), which refer to two or more different characteristics. Finally, it reaches the level of general performance indicators (_GPI_), which include various aspects, such as safety, structure, ride comfort, and environmental aspects. Furthermore, aspects of bridge performance have been analyzed in the recently completed COST Action TU 1406 (quality specifications for roadway bridges, standardization at a European level). The main objective was to develop a guideline for the preparation of quality control plans for road bridges [7; 30; 31; 32]. This action addressed an integrated approach based on the state-of-the-art of bridge performance at the European level by considering (a) technical, (b) sustainability, and (c) socio-economic aspects at three complementary and interrelated levels--(a) component, (b) system and (c) network level [21]. The study of assessment and inspection documents from different European countries [32] revealed that the most commonly used performance indicator at present is the condition index, condition rating, deterioration index, or other nomenclature used by different countries and operators, mainly obtained from visual inspection.