# Decision Support Model for Allocating Maintenance Budgets for Bridges
## 1 Introduction  
Bridges constitute a critical component in transportation networks. They connect intersections while reducing traffic congestion [1]. Due to the imposed traffic load and the presence of environmental criteria, which gradually contribute to bridge degradation, the structure of bridges deteriorates, resulting in worsened conditions [2]. Bridge managers need to carry out maintenance of those bridges periodically to keep their structures in an acceptable condition, and to operate at an acceptable level of service. Decision-makers usually face financial difficulties due to limited budgets to maintain operating existing bridges, along with other impediments to the decision-making process. The distribution of the limited budget among bridges in the network under consideration is a challenging task for maintenance managers since there are several factors that must be taken into consideration other than the physical conditions, which will add to the objective nature of this process. In the presence of limited budget constraints, somebridges must wait until the next budget. The more severe the condition of the component of a bridge, the more it will be prioritized. It must be taken into consideration that the estimated cost for maintenance may vary during the maintenance works, which may result in deferring more less-prioritized bridges components until next year. The difficulty is attributed to determining which bridge should be maintained and which bridge can be undertaken according to one of the future maintenance plans. In the current practice, the main criterion in determining the bridge priority for maintenance and budgeting is the overall condition of the bridge [3]. Thus, condition assessment of bridges is a key task in aiding maintenance activities by providing a concise description of the current state of the bridge in terms of the internal and external damages, which might impact upon the safety and the performance of the structure [4]. In addition to condition assessment, other criteria should be considered in determining the bridge priority for maintenance and budgeting, such as taking into consideration the importance of the traffic of this bridge, the age of the bridge, and many other factors, which will be highlighted and discussed in the literature section. For example, a bridge may have an average condition assessment score but be located in a very important intersection and/or with high traffic volume that requires maintenance, and vice versa. A number of maintenance managers at Saudi Arabia's Ministry of Municipal, Rural Affairs, and Housing, Riyadh, Saudi Arabia were interviewed to examine the current practice of bridge maintenance and prioritization. The interviews concluded that the main limitations of the current practice are in an agreement with the findings of [PERSON] and [PERSON] [5] and can be summarized as follows:  
1. Many bridge rating systems depend on subjective data, which reduce the accuracy of the condition assessment;
2. Neglecting the actual deterioration of the bridges can significantly shorten their lifespan, hence increase their future repair costs. Furthermore, the current bridges' maintenance systems encounter uncertainties associated with the estimated maintenance cost, which results from the selected methodology of the estimation and the available information at the time of preparing the estimate, which makes the selection of bridge maintenance plan uncertain, unrealistic, and risky in terms of cost and schedule. Moreover, the condition assessment, which is mainly based on visual inspections, is greatly influenced by the experience of the bridge inspectors or engineers, accessibility to the structural elements, and the hidden existing defects covered by recent repairs [6]. This paper introduces a new model for bridges' selection for maintenance, considering other criteria in addition to condition assessment.