Rade Hajdin

Methodology and base cost models to determine the total benefits of preservation interventions on road sections in Switzerland

In Switzerland, it is common practice to estimate the total benefits of new roads before they have been built and of road improvement interventions before they have been performed. The guidelines with respect to standardised methodologies and models to be used have been developed (VSS 2003a) and are now in use. It is not yet, however, common practice to estimate the total benefits of road preservation interventions and hence guidelines do not exist with respect to standardised methodologies and models to be used. In order to provide this information, the research package VSS 2004/710-716 was started. This paper presents the methodology and models proposed to be used to evaluate the total benefits of road preservation interventions in Switzerland based on the evaluation and synthesis of existing national and international literature on the relationships between pavement condition and benefits of road use conducted in project 714 of the research package. The use of the methodology and models are demonstrated by determining the optimal intervention strategy for a representative situation in Switzerland. The impact on the optimal intervention strategy of the consideration of multiple stakeholders is investigated.

Potential Use of Inventory Theory to Bundle Interventions in Bridge Management Systems

Before an optimal bridge management strategy can be determined in existing bridge management systems, there must first be a determination of the type and schedule of interventions to be performed on each element of the bridge to achieve a minimal-cost long-term steady state. Once these element-level strategies are known, they are grouped together, or bundled, to develop a management strategy for the bridge. This is currently done with a set of agency rules without regard to whether the bundle of interventions is optimal. Interventions are bundled because it is not desirable to perform interventions on the same bridge in successive years, principally because of user costs. The work discussed here uses inventory theory to bundle interventions on bridges optimally with multiple elements. Two examples are presented. Example 1 shows how a basic joint replenishment model can be used on a multielement bridge to determine optimal management strategies when interventions are bundled and a single-stage policy is used. Example 2 shows how a joint replenishment model with quantity discounts can be used to alleviate some of the problems with a basic joint replenishment model. The optimal management strategy determined in Example 2 is compared with the optimal management strategy determined when interventions are not bundled. Direction for future work is given.

Vulnerability Assessment of Bridges Exposed to Scour

To improve the allocation of funds for the maintenance and risk mitigation of transportation infrastructure, there is a dire need for a simplified, yet sufficiently accurate, methodology to estimate bridge vulnerability to scour. The methodology should make use of existing data and indicate the basic variables needed to assess the vulnerability of bridges located around a future expressway in southeastern Serbia. The first part of the paper discusses the identification of possible modes of bridge failure caused by scouring that depend on soil, structure, and river hydraulic properties. The degradation of soil parameters is assumed to be the main cause of bridge failure. The capacity of a bridge to withstand a certain amount of structural damage governs the direct and indirect costs attributable to bridge failure; the subsequent work zones related to rehabilitation reduce the performance of the whole network. In the second part of the paper, a simulation of the redistribution of traffic flows is described for several possible scenarios; the simulations use state-of-the-art software VISUM, which was developed for computer-aided transportation planning and analysis. The simulated scenarios include the partial and full closure of road links as a result of bridge failures. The simulations confirmed that the most significant contribution to indirect costs stems from the increase in the total travel time of all network users.