STATEMENT OF WORK
RISK-BASED MANAGEMENT OF GUARDRAILS: SITE SELECTION AND UPGRADING
James H. Lambert, Research Assistant Professor, and
Yacov Y. Haimes, Quarles Professor and Center Director
Jeffrey A. Baker, Graduate Student
Center for Risk Management of Engineering Systems, University of Virginia
INTRODUCTION
The following outlines the development of a risk-based aid to the site selection and upgrading of guardrails for engineers, planners, and managers of the Virginia Department of Transportation (VDOT). The goal of the effort is to adopt quantitative and qualitative factors/endpoints and develop the associated cost-benefit-risk tradeoff methodology to support the preliminary screening and subsequent evaluation of guardrail site selection and upgrading with limited available funding. The proposal is in the following parts below: Problem Statement, Purpose and Scope, Methods, Expected Benefits, Schedule, Budget, Deliverables, Preliminary References, and Contractor Qualifications.
PROBLEM STATEMENT
Recent experience of VDOT has suggested that public and transportation-agency values concerning the location and acceptable standards of roadway guardrails are in need of clarification. Moreover, a 1997 customer satisfaction survey identified the concerns of Virginians for adequate guardrails to be high relative to the national norms. The current practice in VDOT Districts for site selection for new guardrails and guardrail upgrades along secondary roads is based on citizen complaints, a general knowledge base of roadway needs from the local engineer, and accident history. Early indications are that most US states use a similar process. Notably Kentucky has developed a hazard-index point system (Kentucky Transportation Center Report KTC-89-39 "Warrants and Guidelines for Installation of Guardrail"). There are hundreds of candidate locations on the thirteen-county secondary system of Richmond District. Particular locations in New Kent and Charles City County have been the focus of a related preliminary study in Richmond District.
PURPOSE AND SCOPE
The goal of the effort is to adopt quantitative and qualitative factors/endpoints and develop the associated cost-benefit-risk tradeoff methodology to support the preliminary screening and subsequent evaluation of guardrail site selection and upgrading with limited available funding. There are four related objectives: (1) A review of the literature and other agencies’ experience of what factors have been considered to be important in the management of roadway safety via guardrails. (2) Adoption of assessment methods and quantitative and qualitative factors/endpoints for the comparison of costs, reductions in risk, and other metrics of guardrail performance. (3) Development of a tradeoff methodology that aids decisionmakers to seek an appropriate balance among the quantitative and qualitative factors/endpoints. (4) Specification and prototype development of databases that support the assessments of costs, risks, and other factors/endpoints related to guardrails.
An increase in tort liability is a potential in the compilation of candidate guardrail locations that later go unfunded. There may be many more worthy locations for guardrails than can be addressed with available funding, however it is in the public interest to have used a sound, auditable process in guardrail location rather than none at all. Uncertainties of data and measurement will be represented in the tradeoff analyses, thus conveying to the public and decisionmakers that the precision of estimates of crash rates and similar parameters is often limited. For example, it may be the rightful discretion of VDOT and local constituents whether to prefer small reductions in risk to large increases in cost, or whether to prefer smaller measurable gains to larger gains known with lesser precision.
METHODS
The effort will consist of the following tasks:
The tasks are described below.
Task 1: Review of Literature
A review and evaluation of past studies, theory and methodology, and databases that support the proposed effort will be performed. Furthermore, the effort will build in part on past responses to surveys by VDOT and other agencies.
Task 2. Formation of Steering Committee and Communication with Resident Engineers
A project steering committee of VDOT engineers and managers will be formed to guide the effort. In addition, as much of the day-to-day experience with the siting of guardrails is within the residencies, a sample of resident engineers will be contacted. Resident engineers who are representative of topographically and otherwise diverse VDOT districts will be interviewed to support (1) the identification of appropriate assessment factors/endpoints and (2) refining the desired features of the developing methodology. The sought balances among factors/endpoints, e.g., costs and risk reductions, in guardrail management will likely be different from region to region. Thus, while the primary case study will be of the Richmond District, additional calibration and input will be solicited from resident engineers outside of the Richmond District.
Task 3. Adoption of Quantitative and Qualitative Factors/Endpoints
The effort will adopt best available models for the assessment of quantitative factors/endpoints from data and engineering judgment (Haimes 1998). Where quantitative models are not available, qualitative measurement scales will be defined. For example, measurement of a qualitative factor can involve the precise natural-language definition of discrete 'highest' to 'lowest' levels for a given attribute. The effort will ensure that an encompassing set of quantitative and qualitative factors/endpoints can be considered and balanced in the screening and subsequent evaluation phase of the methodology.
Task 4. Characterization of Options
The effort will characterize what options are available. Existing guardrails, particularly on the primary system, may conform to standards that have been updated over many years, and the issue may be largely that of upgrading currently installed equipment. However, Virginia is among the top US states in custodianship of secondary roads, where the deployment of guardrails may have been less consistent, and the large issue in the secondary system may be how to identify and evaluate new candidate sites.
The effort will distinguish options in two phases: (1) the preliminary screening of candidate sites, and (2) the evaluation of the smaller set of screened sites based on more detailed analysis. While the same guiding factors/endpoints will be used in both phases (1) and (2), the developing methodology will accommodate and distinguish different levels of the data available for assessment at the two phases.
Task 5. Tradeoff Analysis for Guardrail Management
The effort will develop a methodology for addressing the tradeoffs among costs, risks, and other factors/endpoints with respect to guardrails. The methodology will aid in the selection of what guardrail projects to fund with the limited resources available. An automated spreadsheet for VDOT Districts and Residencies will be developed that facilitates the calculations and trade-off comparison of potential guardrail projects under their jurisdictions.
The graphical interfaces for the balancing of costs, risks, and performance in project comparison and interchange design [Lambert et al. (1998a, b) and Lambert et al. (1999)] are only examples of the direction that is proposed in the current effort. The shortcomings of the current graphical interfaces for guardrail evaluation include (i) an inability to appreciate the merits of a large number of projects, (ii) the complexity of interpretation and evaluation of imprecisely known quantities, and (iii) a tacit encouragement to ignore yet unquantified factors in the comparison of projects. Such shortcomings will be addressed through evolution and revolution of the current designs for graphical tradeoff analyses represented in Lambert et al. (1998a, b) and Lambert et al. (1999).
Task 6. Databases and Demonstration
The effort will develop a case study in which the above methodology is applied to a sample of sites in the Richmond District. The effort will specify and apply databases necessary to quantify the factors/endpoints. Interfaces of the developing software and VDOT's electronic databases (e.g., HTRIS) will be addressed first through internet hyperlinks pointing from the software to available agency databases, and second through the automated access to the databases. To avoid an overwhelming volume of data, the effort will specify data requirements that are appropriate to the capabilities of the residencies.
Task 7. Reports, Presentations, and Workshop
The effort will develop progress and final reports, presentations to VDOT, and a workshop to train VDOT districts and residencies in the developed methodology. Reports, presentations, and software will conform to the publications requirements of the Virginia Transportation Research Council. Documentation and spreadsheets will as well be provided in electronic form and, in coordination with the appropriate information-systems committees of VDOT, via a prototype internet web site at the University of Virginia.
EXPECTED BENEFITS
The benefits of the proposed effort include:
In addition, the reputation of the Virginia Department of Transportation as a leading highway agency will be enhanced through the dissemination of the results of this effort outside the Commonwealth.
SCHEDULE
The tasks described will be performed in fourteen months as described by Figure 1.
Figure 1. Schedule of the fourteenth month effort