Upgrading Bridge Rails on Low-Volume Roads in Iowa

Building on previous research, the goal of this project was to identify significant influencing factors for the Iowa Department of Transportation (DOT) to consider in future updates of its Instructional Memorandum (I.M.) 3.213, which provides guidelines for determining the need for traffic barriers (guardrail and bridge rail) at secondary roadway bridges—specifically, factors that might be significant for the bridge rail rating system component of I.M. 3.213. A literature review was conducted of policies and guidelines in other states and, specifically, of studies related to traffic barrier safety countermeasures at bridges in several states. In addition, a safety impact study was conducted to evaluate possible non-driver-related behavior characteristics of crashes on secondary road structures in Iowa using road data, structure data, and crash data from 2004 to 2013. Statistical models (negative binomial regression) were used to determine which factors were significant in terms of crash volume and crash severity. The study found that crashes are somewhat more frequent on or at bridges possessing certain characteristics—traffic volume greater than 400 vehicles per day (vpd) (paved) or greater than 50 vpd (unpaved), bridge length greater than 150 ft (paved) or greater than 35 ft (unpaved), bridge width narrower than its approach (paved) or narrower than 20 ft (unpaved), and bridges older than 25 years (both paved and unpaved). No specific roadway or bridge characteristic was found to contribute to more serious crashes. The study also confirmed previous research findings that crashes with bridges on secondary roads are rare, low-severity events. Although the findings of the study support the need for appropriate use of bridge rails, it concludes that prescriptive guidelines for bridge rail use on secondary roads may not be necessary, given the limited crash expectancy and lack of differences in crash expectancy among the various combinations of explanatory characteristics

Bridge management from data to policy

Bridge management involves all efforts to build, preserve, and operate bridge networks cost-effectively with an objective to deliver the best value for the public tax dollars spent. The dissertation consists of three complementary studies that address both bridge management policies and condition data that contribute to bridge management practices. This dissertation begins with an overview of federal and state government bridge management efforts taken in conjunction with the federal bridge programs in the last 40 years. While the majority of the states have implemented a BMS, the level of implementation is varied, and the overall input from BMSs to network-level decisions remains minimal. Survey findings from 40 states indicate that federal funding eligibility is the major criterion that impacts state-level bridge management decisions. State transportation agencies need federal guidance on areas such as using decision support tools, implementing BMSs, and improving data quality. The findings from the study are useful to both practitioners and policy makers, and identify challenges and needs for bridge management at both federal and state level. Following the policy study, a statistical comparison of field NBI condition ratings and ratings generated by FHWA's NBI Translator (BMSNBI) algorithm for Iowa bridges is presented. Statistical analysis indicates that the ratings generated by the NBI Translator algorithm are not representative of actual NBI ratings. Results from the research raise questions about the effectiveness of the algorithm. Final study in this dissertation presents a new methodology to predict National Bridge Inventory (NBI) condition ratings from bridge management system (BMS) element condition data, based on Classification and Regression Trees (CART). The proposed methodology achieves significantly better accuracies than other methodologies reported in the literature for the data set used in this study. The CART prediction methodology uses simple and logical conditions of BMS element condition data to predict NBI condition ratings and has potential use for federal and state transportation agencies to summarize bridge condition data.</p

Bridge management from data to policy

Bridge management involves all efforts to build, preserve, and operate bridge networks cost-effectively with an objective to deliver the best value for the public tax dollars spent. The dissertation consists of three complementary studies that address both bridge management policies and condition data that contribute to bridge management practices. This dissertation begins with an overview of federal and state government bridge management efforts taken in conjunction with the federal bridge programs in the last 40 years. While the majority of the states have implemented a BMS, the level of implementation is varied, and the overall input from BMSs to network-level decisions remains minimal. Survey findings from 40 states indicate that federal funding eligibility is the major criterion that impacts state-level bridge management decisions. State transportation agencies need federal guidance on areas such as using decision support tools, implementing BMSs, and improving data quality. The findings from the study are useful to both practitioners and policy makers, and identify challenges and needs for bridge management at both federal and state level. Following the policy study, a statistical comparison of field NBI condition ratings and ratings generated by FHWA's NBI Translator (BMSNBI) algorithm for Iowa bridges is presented. Statistical analysis indicates that the ratings generated by the NBI Translator algorithm are not representative of actual NBI ratings. Results from the research raise questions about the effectiveness of the algorithm. Final study in this dissertation presents a new methodology to predict National Bridge Inventory (NBI) condition ratings from bridge management system (BMS) element condition data, based on Classification and Regression Trees (CART). The proposed methodology achieves significantly better accuracies than other methodologies reported in the literature for the data set used in this study. The CART prediction methodology uses simple and logical conditions of BMS element condition data to predict NBI condition ratings and has potential use for federal and state transportation agencies to summarize bridge condition data

Evaluating the Effectiveness of Temporary Work-Zone Pavement Marking Products [Project Title from Cover]

Work zones by nature present transitions and changes to motorists\u2019 expectations. Given these conditions, providing proper guidance to motorists is critical. With respect to pavement markings, the challenge is to provide sufficient markings but in a temporary setting. Various pavement-marking products are currently in use within work zones; however, their effectiveness and cost can vary widely. This research evaluated the effectiveness of several common removable pavement marking products in terms of daytime presence, retroreflectivity, and removability. The evaluation was completed on an active work zone in central Iowa and included both white and yellow edge-line markings within the taper and crossover sections of a work zone. Presence was evaluated in terms of the amount of product remaining at the end of the evaluation period. Retroreflectivity was measured using a 30 meter geometry retroreflectometer. Product removal was evaluated in terms of internal tape strength, adhesive bond, and the amount of discernible markings after removal based on the American Association of State Highway and Transportation Officials (AASHTO) National Transportation Product Evaluation Program (NTPEP). Findings showed that the temporary pavement marking tapes performed satisfactorily over the 56 day time period with the exception of materials placed over very rough surfaces (rumble strip) or where vehicle maneuvering directly over the marking led to tearing or similar damage. Based on these findings, the research team recommends that agencies who are not currently specifying the use of temporary pavement marking tape products on temporary roadway surfaces (eg. within the cross-over area of a work zone which will be removed after the project) should reconsider their policy. The cross-over area receives the majority of wear, due to traffic weaving, and these markings are placed over a variety of, smooth to very rough, pavement surface conditions. Removable paint products are rapidly evolving and are a potentially promising alternative in terms of installation, cost, and removal (no scaring) which should be further investigated