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R27-242, Accelerated bridge construction (ABC) methods have been increasingly used in recent years to reduce the impact of construction operations on traffic and mobility. ABC methods, however, often require a higher initial cost, more planning, and additional design coordination. Several tools have been developed to assist decision-makers in the selection of conventional staged construction or ABC methods based on bridge characteristics and requirements. Most of these existing tools, however, are qualitative and depend on the subjective opinion of decision-makers/experts. Accordingly, there is a need for additional research to develop quantitative tools for generating reliable cost estimates for conventional and accelerated bridge construction methods. This report presents the findings of a research project funded by the Illinois Department of Transportation (IDOT) to develop a decision support tool (DST) that IDOT can use to estimate and compare the cost of all bridge construction methods, including conventional staged construction and ABC methods. This project has four objectives. The first objective is to develop a qualitative DST that can be used by IDOT planners and decision-makers to identify all feasible bridge construction methods for any bridge project based on its specific characteristics, requirements, and constraints. The second objective is to create a quantitative cost-estimating DST that can be used to accurately estimate construction, road user, maintenance and rehabilitation, and life cycle costs for all feasible construction methods including conventional and ABC methods. The third objective is to develop guidance for the user interface of the developed DST to explain how it can be used to compare and rank all feasible bridge construction methods based on their individual performance in design, construction, road user, and maintenance and rehabilitation costs. The fourth objective is to evaluate the performance and accuracy of the developed quantitative DS

The American Association of State Highway and Transportation, Officials (AASHTO) publication titled A Policy, on Geometric Design of Highways and Streets (Green, Book) provides guidance to the designer by referencing, a recommended range of values for critical dimensions, for the design of new alignments and those undergoing, major reconstruction. These guidelines permit sufficient, flexibility to encourage independent designs for specific, situations. The approach allows the designer to use, flexibility to introduce “lower than typical” design values, for a specific element to address an impacted area. This, process allows for adjusting almost every aspect of the, geometric design and may require both state and federal, approval. Use of design flexibility may include use of a, design exception. The current version of the Indiana Design, Manual (IDM) provides and promotes some level of, flexibility, particularly on non-NHS routes. The selection, of design criteria for a transportation project is typically, screened by the highway system the project is located, on, functional classification, area type, forecasted traffic, data and classification of project type. The use of design, exceptions is one way to obtain design flexibility. Design, exceptions require appropriate level of justification.

SPR-3404, The American Association of State Highway and Transportation Officials (AASHTO) publication titled A Policy on Geometric Design of, Highways and Streets (Green Book) provides guidance to the designer by referencing a recommended range of values for critical, dimensions for the design of highway facilities. For various reasons, it may be necessary to design a section of highway with substandard, values for some elements. Such design exceptions require appropriate assessment and justification of the potential impacts to highway, safety and operations. This study was performed to develop a guideline for design exceptions. The guideline for development and, evaluation of design exception projects was developed and presented. The guideline outlines the steps for developing and evaluating, design exception projects. The potential impacts of design exception elements to highway safety and operations are listed for the 13, controlling criteria to provide designers with important and easy to use information. The possible counter measures for each of the, controlling criteria are listed in a one-page table for easy reference. The proposed safety evaluation process was presented in terms of, safety impacts of individual substandard elements as well as the combined impacts of the substandard elements. An Excel based, computer program was developed for life-cycle benefit-cost analysis of design exception projects. A decision on design exceptions can, thus be made rationally with the recommended guideline and methods.