Accident Analysis and Prevention 38 (2006) 925–935 Synthesis of quantitative and qualitative evidence for accident analysis in risk-based highway planning James H. Lambert ∗ , Kenneth D. Peterson, Nilesh N. Joshi Center for Risk Management of Engineering Systems, Department of Systems and Information Engineering, University of Virginia, Charlottesville, VA 22904, USA Received 22 July 2005; received in revised form 14 December 2005; accepted 11 March 2006 Abstract Accident analysis involves the use of both quantitative and qualitative data in decision-making. The aim of this paper is to demonstrate the synthesis of relevant quantitative and qualitative evidence for accident analysis and for planning a large and diverse portfolio of highway investment projects. The proposed analysis and visualization techniques along with traditional mathematical modeling serve as an aid to planners, engineers, and the public in comparing the benefits of current and proposed improvement projects. The analysis uses data on crash rates, average daily traffic, cost estimates from highway agency databases, and project portfolios for regions and localities. It also utilizes up to two motivations out of seven that are outlined in the Transportation Equity Act for the 21st Century (TEA-21). Three case studies demonstrate the risk-based approach to accident analysis for short- and long-range transportation plans. The approach is adaptable to other topics in accident analysis and prevention that involve the use of quantitative and qualitative evidence, risk analysis, and multi-criteria decision-making for project portfolio selection. © 2006 Elsevier Ltd. All rights reserved. Keywords: Multi-criteria decision-making; Accident analysis; Crash rate; Transportation planning; Multiobjective combinatorial optimization 1. Introduction Decision-makers at district and state transportation agen- cies in the United States are faced with the tasks of allocat- ing limited public funds among potential highway improve- ment projects and subsequently determining the order in which selected projects should be undertaken. There are many thou- sands of projects competing for these funds. In the Transporta- tion Equity Act for the 21st Century (TEA-21, 2004), trans- portation agencies are required to consider seven motivations in making decisions for projects that qualify for federal funding. TEA-21 is an extension of the initiatives established in the Inter- modal Surface Transportation Efficiency Act of 1991 (ISTEA). TEA-21 combines the continuation of existing programs with new initiatives to address issues that include safety, protection of the natural environment, and economic growth through effi- cient and flexible transportation. The 6-year authorizations for the highway (including highway safety) and transit programs in TEA-21 total approximately US$ 218 billion. In late 2005, TEA- ∗ Corresponding author. Tel.: +1 434 982 2072; fax: +1 434 924 0865. E-mail address: lambert@virginia.edu (J.H. Lambert). 21 was reauthorized as the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA- LU). The seven project motivations mentioned in the TEA-21 act are summarized as: safety/security, accessibility/mobility, operations, system preservation, environment, intermodal con- nectivity, operations, and economic development. In addition to the categorical TEA-21 motivations, transporta- tion agencies consider quantitative evidence of crash rates and traffic exposure in project planning and programming. This paper develops a risk-based approach for synthesiz- ing quantitative and qualitative evidence for accident analysis in planning major highway infrastructure investment projects. The scope of the paper includes: identifying useful metrics for comparing diverse highway projects; developing an interface for displaying project portfolio information, including quantitative and qualitative factors; and presenting several case studies with short- and long-range plans from the state of Virginia. The organization of this paper is as follows. Section 2 reviews the literature related to resource allocation to projects that can reduce higher crash rates; these include existing prioritization methods used by several transportation agencies. Section 3 describes the approach for accident analysis and risk-based high- way planning, which is based on combining quantitative and 0001-4575/$ – see front matter © 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.aap.2006.03.003