Showing papers in "NCHRP Report in 2014"

Characterization of Cementitiously Stabilized Layers for Use in Pavement Design and Analysis

Abstract: This report presents information on the characterization of cementitiously stabilized layers and the properties that influence pavement performance. It also contains recommended performance-related procedures for characterizing these layers and performance-prediction models for incorporation into the mechanistic–empirical pavement analysis methods. Individual chapters highlight pavement distresses of hot-mix asphalt pavements and concrete pavements, laboratory tests and model development, and model calibration. The material contained in the report will be of immediate interest to state materials, pavement, and construction engineers and others involved in the different aspects of pavement design and construction.

Field Performance of Warm Mix Asphalt Technologies

Abstract: This report compares material properties and field performance of warm mix asphalt (WMA) and control hot mix asphalt (HMA) pavement sections constructed at 14 locations across the United States between 2006 and 2010. The specific objectives of the project were to (1) compare the short-term performance of WMA and control HMA pavements, (2) examine relationships among engineering properties of WMA binders and mixes and the field performance of pavements constructed with WMA technologies, (3) compare production and laydown practices between WMA and HMA pavements, and (4) provide relative emissions measurements of WMA technologies and conventional HMA technologies. Performance and material property data were obtained from 14 field projects. Each of the 14 projects included single- or multiple-WMA technology pavement sections and an HMA control section. A total of 12 WMA technologies were investigated. All projects used “drop in” WMA mix designs where the WMA technology was used with an existing HMA mix design with no significant changes to the binder content or other aspects of the mix design. Except for the reduced mixing and compaction temperatures for WMA, there were no substantial differences in the production and laydown practices of WMA and HMA. In-service performance of WMA and HMA in all projects was virtually identical, with little or no rutting, no evidence of moisture damage, and very little indication of transverse or longitudinal cracking. Energy use, plant and paver emissions, and worker exposure to fumes were extensively measured at three multiple-WMA technology projects. Compared to HMA, the reduced temperatures used in WMA production and laydown yielded lower energy consumption and emissions and reduced worker exposure to respirable fumes. Overall, then, no penalties and some potential benefits were observed in the short term when WMA replaced HMA. The key finding of laboratory testing of WMA binders and mixtures from the projects sampled at construction was the expected lower stiffness of the WMA materials that would have potential effects on pavement rutting and cracking. However, the equivalent performance of the WMA and HMA pavement sections over several years of service suggests that these differences in material properties, when present, were not great enough to affect the relative performances of HMA and WMA. This report fully documents the research in two parts bound in one report. Part 1 includes an appendix on Falling Weight Deflectometer Testing; Part 2 includes an appendix on Documenting Emissions and Energy Reductions of WMA and Conventional HMA During Plant and Paving Operations.

Estimating Bicycling and Walking for Planning and Project Development: A Guidebook

Abstract: This guidebook contains methods and tools for practitioners to estimate bicycling and walking demand as part of regional-, corridor-, or project-level analyses. The methods are sensitive to key planning factors, including bicycle and pedestrian infrastructure, land use and urban design, topography, and sociodemographic characteristics. The planning tools presented in this guidebook include some entirely new methods as well as some existing methods found to have useful properties for particular applications. The tools take advantage of existing data and the capabilities present in GIS methods to create realistic measures of accessibility which are a critical determinant of bicycle, pedestrian, and even transit mode choice. The publication includes a CD-ROM (CRP-CD-148) containing a GIS Walk Accessibility Model, spreadsheets, and the contractor’s final report, which documents the research and tools that operationalize the methods described in the guidebook. The CD-ROM is also available for download from TRB’s website as an ISO image. The guidebook should be of value to transportation practitioners either directly interested in forecasting bicycling or walking activity levels or accounting for the impact of bicycle or pedestrian activity in support of broader transportation and land use planning issues.

Guidebook on Pedestrian and Bicycle Volume Data Collection

Abstract: NCHRP Report 797: Guidebook on Pedestrian and Bicycle Volume Data Collection is directed to practitioners involved in collecting non-motorized count data. The Guidebook (1) describes methods and technologies for counting pedestrians and bicyclists, (2) offers guidance on developing a non-motorized count program, (3) gives suggestions on selecting appropriate counting methods and technologies, and (4) provides examples of how organizations have used non-motorized count data to better fulfill their missions. The research behind the Guidebook can be found on the TRB website as NCHRP Web-Only Document 205: Methods and Technologies for Pedestrian and Bicycle Volume Data Collection (NWOD 205). NWOD 205 includes the results of the testing and evaluation of a range of automated count technologies that capture pedestrian and bicycle volume data.

Evaluation of the Moisture Susceptibility of WMA Technologies

Abstract: Over the past decade, the use of warm mix asphalt (WMA) for asphalt pavement construction has increased in the United States. However, questions remain about the long-term performance and durability of WMA pavements. One key issue is the moisture susceptibility of WMA pavements. Concerns about WMA moisture susceptibility include the possibility that aggregates will be inadequately dried at lower production temperatures and the fact that several WMA technologies introduce additional moisture in the production process. The objectives of National Cooperative Highway Research Program (NCHRP) Project 9-49 were to (1) assess whether WMA technologies adversely affect the moisture susceptibility of asphalt pavements and (2) develop guidelines for identifying and limiting moisture susceptibility in WMA pavements. The research was conducted through coordinated laboratory and field experiments that investigated the potential for moisture susceptibility in WMA compared to hot mix asphalt (HMA). Design of the experiments was guided by a survey of the state departments of transportation and industry on WMA pavement construction and performance. The survey identified no instances of moisture damage to WMA pavements in service through 2010. This negative finding is supported by the results of recently completed NCHRP Project 9-47A, which conducted intensive evaluations of WMA pavements constructed across the United States between 2006 and 2011. Project 9-49 then focused on development of guidelines for WMA mix design and quality control to identify and minimize any possibility of moisture susceptibility. The laboratory experiments evaluated (1) laboratory-conditioning protocols for WMA before moisture susceptibility testing, (2) the ability of standard test methods to detect moisture susceptibility of WMA, and (3) potential differences in WMA moisture susceptibility measured on laboratory-mixed and -compacted specimens; plant-mixed, laboratory-compacted specimens; and plant-mixed, field-compacted cores. The guidelines are presented in the form of a workflow of conditioning protocols and standard test methods that first assess the potential moisture susceptibility of a WMA mix design or field mixture and then recommend remedies to minimize such susceptibility. Specific test thresholds in the guidelines are based on the results of testing of WMA from field projects in Iowa, Montana, New Mexico, and Texas. This report fully documents the research and includes the following Appendixes: Appendix A, Laboratory Conditioning Experiment; Appendix B, Moisture Conditioning Experiment; Appendix C, Performance Evolution Experiment; Appendix D, Construction Reports and Performance of Field Projects; Appendix E, Mixture Volumetrics; Appendix F, Proposed Draft Revisions to the Appendix to AASHTO R 35; Appendix G, Future Work Plan to Evaluate Moisture Susceptibility of HMA and WMA; and Appendix H, Statistical Results. Appendix F is included herein. Appendixes A—E, G, and H are available on the TRB website.

Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report

Abstract: Major trends affecting the future of the United States and the world will dramatically reshape transportation priorities and needs. The American Association of State Highway and Transportation Officials established the National Cooperative Highway Research Program (NCHRP) Project 20-83 research series to examine global and domestic long-range strategic issues and their implications for departments of transportation (DOTs) to help prepare the DOTs for the challenges and benefits created by these trends. NCHRP Report 750: Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report is the second report in this series. This report presents guidance on adaptation strategies to likely impacts of climate change through 2050 in the planning, design, construction, operation, and maintenance of infrastructure assets in the United States (and through 2100 for sea-level rise).In addition to the practitioner’s guide and research report, this project also developed the following items: 1) a software tool that runs in common web browsers and provides specific, region-based information on incorporating climate change adaptation into the planning and design of bridges, culverts, stormwater infrastructure, slopes, walls, and pavements; 2) tables that provide the same information as the previously mentioned software tool, but in a spreadsheet format that can be printed; and 3) two spreadsheets that illustrate examples of the benefit-cost analysis of adaptation strategies discussed in Appendix B of Part I of NCHRP Report 750, Volume 2. These three items are available on a CD-ROM (CRP-CD-146) that is included with a print version of the report. The CD-ROM is also available for download from TRB’s website as an ISO image.

Proposed Guideline for Reliability-Based Bridge Inspection Practices

Abstract: This report presents a proposed guideline for reliability-based bridge inspection practices and provides two case studies of the application of the proposed Guideline. The guideline describes a methodology to develop a risk-based approach for determining the bridge inspection interval according to the requirements in the “Moving Ahead for Progress in the 21st Century Act (MAP-21)” legislation. The goal of the methodology is to improve the safety and reliability of bridges by focusing inspection efforts where most needed and optimizing the use of resources. The report includes two parts: Part I—Proposed Guideline for Reliability-Based Bridge Inspection Practices and Part II—Final Research Report: Developing Reliability-Based Inspection Practices that documents the entire research effort. The material in this report will be of immediate interest to bridge engineers.

Applying GPS Data to Understand Travel Behavior, Volume I: Background, Methods, and Tests

Abstract: With the high costs associated with primary data collection, methods to improve the use and accessibility of newer sources of data such as Global Positioning System (GPS) data can benefit many transportation practitioners. GPS data can have multiple uses beyond traditional applications such as estimates of speed and travel times. GPS-related data that have been collected from automatic vehicle location systems, from highway sensors, as supplemental information to traditional travel surveys, and via passive technologies [e.g., Bluetooth, radio frequency identification (RFID), and smartphones] have shown promise for additional planning purposes. Some challenges to increased use of GPS data include addressing data bias; balancing precision, coverage, and confidentiality; resolving institutional issues such as data ownership; and addressing the complexity of combining these data with other sources to discern behavioral relationships. This report provides guidelines on the use of multiple sources of GPS data to understand travel behavior and activity. The guidelines are intended to provide a jump-start for processing GPS data for travel behavior purposes and provide key information elements that practitioners should consider when using GPS data. The report is structured in two volumes. Volume 1 presents the methods used and results of tests conducted. Volume II translates the results of the tests conducted into guidelines for planners and researchers to implement these procedures.

Superelevation Criteria for Sharp Horizontal Curves on Steep Grades

Abstract: Sharp, horizontal curves on steep downgrades represent a potential safety concern for vehicles, especially heavy vehicles. Examples where this combination may occur are interchange ramp movements, curves on mountainous roads, or high-speed downgrade curves on controlled-access roadways. At these locations, the complicating factors of grade, pavement cross slope, and pavement friction fully tax the driver’s ability to provide correct vehicle positioning without compromising control of the vehicle. Superelevation criteria, horizontal curvature, and other associated geometric criteria needed to be developed for situations where steep grades are located on sharp horizontal curves. This report provides superelevation criteria for horizontal curves on steep grades. A series of field studies and vehicle dynamics simulations were undertaken to investigate combinations of horizontal curve and vertical grade design. Three classes of passenger vehicles and three classes of trucks were considered for safety analysis. The report provides design guidance based on the analyses for sharp horizontal curves on steep grades.

Bridge System Safety and Redundancy

Abstract: This report develops a method to calibrate system factors that can be applied during the design and load capacity evaluation of highway bridges to account for bridge redundancy and system safety The proposed system factors can be used during the design and safety assessment of bridges subjected to distributed lateral load being evaluated using the displacement-based approach specified in the AASHTO Guide Specifications for LRFD Seismic Bridge Design or the traditional force-based approach Also, the report presents system factors calibrated for application with bridge systems subjected to vertical vehicular loads

Best Practices for Crack Treatments for Asphalt Pavements

Abstract: Crack sealing and crack filling are widely used treatments for maintenance of asphalt pavements. However, successful crack sealing and crack filling applications continue to be viewed as an art. When not properly applied, these pavement preservation treatments can result in early failures and costly corrective maintenance for highway agencies. Although much research has been performed in the United States and abroad on the materials, techniques, and designs for crack sealing and crack filling, variability in the current state of the practice regarding construction techniques and the resulting effectiveness of crack sealing and crack filling have not been investigated. This report presents best practices for crack treatments for asphalt pavements developed through a critical review of the current states of the art and practice. The research included a critical review of the worldwide literature on crack sealing and filling, with emphasis on identifying current best practices. A survey of state, local, and provincial highway agencies was then conducted to fill gaps in the results of the literature review. This report fully documents the research and includes chapters on the current states of the art and practice that support the chapter discussing the selected best practices. It will be of interest to engineers in public agencies and industry with responsibility for construction and maintenance of asphalt pavements.

A Guide for Public Transportation Pandemic Planning and Response

Abstract: A pandemic can be described as a global disease outbreak Addressing decision-making challenges in pandemic response in the transportation context is a multi-dimensional task, involving not only transportation/transit organizations, but health organizations, emergency management agencies, and communications outlets as well This guide is designed to outline broad guidance on dealing with preparedness planning for pandemics and other infectious diseases such as seasonal flu It provides information, tools, tips, and guidance on where to find up-to-date recommendations from federal agencies and other resources, prior to and during a pandemic While primarily intended for small urban and rural transit organizations, this guide can be used by all types and sizes of transportation agencies and organizations with different levels of preparedness for pandemics

Applying GPS Data to Understand Travel Behavior, Volume II: Guidelines

Abstract: With the high costs associated with primary data collection, methods to improve the use and accessibility of newer sources of data such as Global Positioning System (GPS) data can benefit many transportation practitioners. GPS data can have multiple uses beyond traditional applications such as estimates of speed and travel times. GPS-related data that have been collected from automatic vehicle location systems, from highway sensors, as supplemental information to traditional travel surveys, and via passive technologies [e.g., Bluetooth, radio frequency identification (RFID), and smartphones] have shown promise for additional planning purposes. Some challenges to increased use of GPS data include addressing data bias; balancing precision, coverage, and confidentiality; resolving institutional issues such as data ownership; and addressing the complexity of combining these data with other sources to discern behavioral relationships. This report provides guidelines on the use of multiple sources of GPS data to understand travel behavior and activity. The guidelines are intended to provide a jump-start for processing GPS data for travel behavior purposes and provide key information elements that practitioners should consider when using GPS data. The report is structured in two volumes. Volume 1 presents the methods used and results of tests conducted. Volume II translates the results of the tests conducted into guidelines for planners and researchers to implement these procedures.

Analytical Travel Forecasting Approaches for Project-Level Planning and Design

Abstract: This report is an update to NCHRP Report 255: Highway Traffic Data for Urbanized Area Project Planning and Design and describes methods, data sources, and procedures for producing travel forecasts for highway project-level analyses. The report provides an evaluation of currently used methods and tools. The report also includes appropriate information sources and system-level methods (ranging from readily available practices to advanced practices) to address a variety of project development purposes, needs, and impacts. The report is intended to be used by transportation planning, operations, and project development staff to better support planning, design, and operations recommendations. The report is accompanied by a CD-ROM (CRP-CD-143) providing spreadsheet tools developed for project-level analyses as well as appendices from the contractor’s final report.

Development and Calibration of AASHTO LRFD Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals

Abstract: This report presents proposed AASHTO load and resistance factor design (LRFD) specifications for structural supports for highway signs, luminaires, and traffic signals. The proposed specifications are arranged in three divisions: (1) design according to LRFD methodology; (2) construction, including material specifications, fabrication, and installation; and (3) asset management, including inventory, inspection, and maintenance. In addition, the report provides details regarding the reliability calibration process and results. Sixteen comprehensive design examples were developed to illustrate the application of the new specifications. The report includes the Research Report, which documents the entire research effort, and the Calibration Report (i.e., Appendix A). Appendix B: AASHTO LRFD Specifications will be published by AASHTO. Other appendices are not published but are available on the TRB website. These appendices are titled as follows: Appendix C: Design Examples; Appendix D: Survey Results; and Appendix E: Fatigue Resistance Comparisons.

Guide for Design Management on Design-Build and Construction Manager/General Contractor Projects

Abstract: While the traditional design-bid-build (DBB) approach to project delivery remains prevalent among state departments of transportation (DOTs) and other owners of transportation facilities, some agencies have been selectively adopting alternative delivery methods that increase collaboration among the owner, designer, and constructor. Under the design-build (D-B) process, for example, the designer and constructor act as a unified team to deliver a completed project at a set price. Under a construction manager-at-risk (CMR) process, designer and constructor are engaged separately by the owner (as is the case under DBB), but the constructor is involved from the earliest stages of the design process; the designer and constructor are expected to work collaboratively to deliver a project that meets the owner’s requirements. Some agencies have adopted the term Construction Manager/ General Contractor (CM/GC) for a method that is generally similar to CMR but has more effectively facilitated the reallocation of risk among owner, constructor, and designer; and does not restrict the primary contractor’s performance of work tasks. (As used in this research, CM/GC was understood to include CMR.) Experience has shown that agency policies used to develop and administer traditional design contracts (that is, under DBB) are inadequate for these alternative delivery methods. The objective of this project was to develop a guide to effective design-management practices for owners using CM/GC or D-B. The research team reviewed recent experiences of DOTs and other public agencies regarding design management practices used on projects developed under CM/GC, D-B, and similar methods for project delivery. The team also investigated relevant experience from other construction industry segments. Considering such issues as liability and responsibility in CM/GC and D-B project development and measures of effectiveness for design management, the team developed a framework characterizing principal areas where owners’ design management practices under CM/GC and D-B project delivery processes are likely to influence project success and specific guidance for successful design management. The product is a guidebook for state DOTs and other transportation agencies on design management under CM/GC and D-B project delivery. The guidance is supplemented by case studies of projects successfully developed by several DOTs. This document is written to assist agency staff responsible for management oversight of facilities developed using CM/ GC and D-B and other such alternative procurement strategies.

Evaluation of the 13 Controlling Criteria for Geometric Design

Abstract: This report describes the impact of the controlling roadway design criteria on safety and operations for urban and rural roads. In 1985, the FHWA designated 13 specific design elements as controlling criteria for roadway design. The 13 controlling criteria are (1) design speed, (2) lane width, (3) shoulder width, (4) bridge width, (5) structural capacity, (6) horizontal alignment, (7) vertical alignment, (8) grade, (9) stopping sight distance, (10) cross slope, (11) superelevation, (12) vertical clearance, and (13) horizontal clearance. Federally assisted highway construction and reconstruction projects must meet the established design criteria for these elements, or a formal design exception must be prepared and approved. Different procedures apply to rehabilitation projects, but these design elements are still key considerations in design. Since their designation, the 13 controlling criteria and their application have not been reconsidered as new knowledge has been gained about the relationships between geometric design elements and safety and operations. In this research project, the research team investigated what is known about the safety and operational effects of the 13 controlling and other important geometric design criteria. Several small studies were done to augment the information found in the literature. This information was used to assess the sensitivity of safety and operations to design decisions for these criteria for different types of roads. The research also addressed how to reduce confusion related to the definitions of the controlling criteria. The use of the controlling criteria in design exception processes was also explored, including through interviews with state department of transportation (DOT) personnel. This report will be useful to geometric designers and those responsible for reviewing designs, particularly in agencies that are transitioning away from “standards-based design.”

Strategic Issues Facing Transportation, Volume 6: The Effects of Socio-Demographics on Future Travel Demand

Abstract: Major trends affecting the future of the United States and the world will dramatically reshape transportation priorities and needs. The American Association of State Highway and Transportation Officials established the NCHRP Project 20-83 research series to examine global and domestic long-range strategic issues and their implications for departments of transportation (DOTs) to help prepare the DOTs for the challenges and benefits created by these trends. This publication is the sixth report in this series. This report presents the results of research on how socio-demographic changes over the next 30 to 50 years will impact travel demand at the regional level. The research approach involved identifying a number of plausible future scenarios and development of a systems dynamic model that simulates the demographic evolution of a regional population starting from a baseline of the 2000 census and spanning a period of 50 years. The four future scenarios were developed using a Strategic Assumptions Surfacing and Testing (SAST) technique and include the following: (1) Momentum: gradual change without radical shifts; (2) Technology Triumphs: technology solves many present-day problems; (3) Global Chaos: a collapse in globalism and sustainability, and (4) Gentle Footprint: a widespread shift to low-impact living. The model does not predict which scenario is most likely; instead it predicts how travel demand will change under each of the five sectors: socio-demographics, travel behavior, land use, employment, and transportation supply. The accompanying CD (CRP-CD-152) contains the Impacts 2050 software tool, the user’s guide, a PowerPoint presentation about the research, and the research brief. The Impacts 2050 tool enables modeling of changes in these sectors due to socio-demographic changes, the interplay between sectors, and external factors such as attitudes and technology. This report will help transportation decision makers understand how the population may change over time, how socio-demographic changes will affect the ways people travel, and the kinds of transportation modes and infrastructure that will be needed.

Median Cross-Section Design for Rural Divided Highways

Abstract: This report presents guidelines for designing typical cross-sections for medians on new and existing rural freeways and divided highways. The report examines the interrelationships between median width, median slope, and the use of median barrier on crash risk and severity. The AASHTO Policy on Geometric Design of Highways and Streets contains general median width and median side-slope design guidance that has remained unchanged for many years. However, changes have occurred in the vehicle fleet, travel speeds, and traffic volumes that warrant further examination of this guidance. Concern with rollover crashes has caused many state departments of transportation (DOTs) to flatten their depressed medians. More recently, highly visible cross-median crashes have caused many state DOTs to increase their use of median barrier beyond the recommendations in the AASHTO Roadside Design Guide. There is speculation that flatter medians have contributed to the cross-median problem, but the data do not present a clear picture. Installation of median barrier reduces the number of cross-median crashes but increases the number of fixed-object crashes. Understanding how different median cross-section designs influence different types of crashes is vital in making safe and cost-effective decisions for state design standards and for project design. In National Cooperative Highway Research Program (NCHRP) Project 22-21, the research team updated the survey of state practice developed in NCHRP Project 17-14, including the types of barrier being installed and the policies for their installation. The research team also compiled information on typical median cross-sections for new construction and reconstruction projects. Based on the literature, the researchers identified design, traffic, and human factors that influence median and roadside safety. The research team then collected field data to assess the safety and cost-effectiveness of various median cross-section designs. Simulations of median encroachments were also made to evaluate the contributions of the various factors to cross-median crashes. This report should be useful to designers and safety analysts, particularly those responsible for agency standards.

Long-Term Performance and Life-Cycle Costs of Stormwater Best Management Practices

Abstract: A wide range of treatment controls (commonly known as “best management practices” or BMPs) have been developed to manage stormwater. Treatment BMPs use various processes to mitigate the impacts of pollutants and altered hydrology; for example, by attenuating the flow or reducing the volume of stormwater or by reducing pollutants with physical, biological, or chemical processes. This report provides information on long-term performance and life-cycle costs for highway-related stormwater BMPs. Information was gathered via literature review, survey of departments of transportation (DOTs), and interviews with practitioners. Information for treatment BMPs was derived from DOT studies and the International BMP Database. The International BMP Database contains performance records for treatment BMP evaluations throughout the United States. The research included conducting a large number of computer simulations using the U.S. EPA’s Stormwater Management Model (SWMM) to quantify runoff volume reduction through the BMP. The report is accompanied by a CD-ROM (CRP-CD-153) containing a BMP evaluation tool in a spreadsheet format as a computational aid that provides average annual performance and whole life costs for treatment BMPs. A guide (Planning Tool Handbook) is provided as Appendix F to quickly orient the user to the basic functions of the tool provided on the CD-ROM. The report will be of interest to state DOT highway design and environmental practitioners.

Measuring and Removing Dissolved Metals from Stormwater in Highly Urbanized Areas

Abstract: This report presents prototype best management practices for the removal of dissolved metals in stormwater runoff. Three conceptual configurations are presented in detail: two vault system configurations for urban and rural settings, and an inlet scupper with media for bridge deck drainage systems. The report also includes standard protocols to accurately measure the levels of dissolved metals in stormwater. Practical guidance on the use of these protocols is provided in an appendix to the final report. The report is accompanied by an Excel spreadsheet on CD (CRP-CD-147) designed to assist in sizing the filter bed in the vaults and the bridge deck inlet scupper. The report is suitable for immediate application by transportation practitioners in planning, design, and construction, particularly in areas where receiving waters are most susceptible to the impacts of dissolved metals.

Design Methods for In-Stream Flow Control Structures

Abstract: This report presents design guidelines for in-stream flow control structures that are often used to limit lateral migration and reduce bank erosion. The guidelines include a description of conditions under which in-stream flow control structures are either successful or not effective in providing protection against erosion and scour and in performing applicable habitat restoration functions. Unlike rip-rap, which strengthens the bank to withstand the applied hydrodynamic forces, in-stream flow control structures alter the stream-flow patterns to shift the high-velocity thread away from the bank. This report will be valuable to hydraulic engineers by facilitating the use of an alternative method to reduce stream-bank erosion and scour.

Guide to Accelerating New Technology Adoption through Directed Technology Transfer

Abstract: Technology transfer (T²) is an integral function in the process that advances innovation and brings new ideas to transportation organizations. This report presents a framework and guidance on how to use T² to guide and accelerate innovation within a state department of transportation or other such agency. Chapter 1 of this guide provides background on innovation adoption and T²; introduces the Innovation Adoption Process, guided T², and its 10 components; and explores how different users can approach the remaining chapters of the guide. Chapters 2 through 11 of the guide are focused on assisting users with the guided T² phase of the Innovation Adoption Process. Each chapter details one of 10 components of guided T². The guide includes illustrative examples of innovations in organization and policy as well as design, materials, and operations.

A Guide to Regional Transportation Planning for Disasters, Emergencies, and Significant Events

Abstract: This report helps transportation stakeholders in the public and private sectors, as well as non-transportation stakeholders, such as emergency managers and first responders, better understand transportation’s important role in planning for multijurisdictional disasters, emergencies, and major events. The guide sets out foundational planning principles and uses examples, case studies, tips, tools, and suggested strategies to illustrate their implementation. The research (literature review, survey, and interviews) conducted for this project discovered multijurisdictional transportation planning for disasters, emergencies, and significant events taking place in many locations across the country, in many different institutional frameworks. Such planning shares precepts of communication and collaboration, supported by eight basic principles that enable communities to better recover after a major disruption. Effective planning is comprehensive, cooperative, informative, coordinated, inclusive, exercised, flexible, and continuous. These principles connect the many disciplines, levels of government, and private, nonprofit, and public-sector agencies that contribute to a good community plan. They provide a shared vocabulary for a collaborative effort that promises sound preparation, effective response, and rapid recovery.

Assessing Productivity Impacts of Transportation Investments

Abstract: This report presents a methodology for analyzing productivity effects of transportation system improvements The analysis is intended to inform decisionmakers—for example, regional transportation planning agencies, local-government agencies, and elected officials—making choices among alternative investments that may yield a variety of benefits The methodology involves first screening investments to identify those for which a relatively simplified analysis may be helpful; those requiring more extensive analysis require application of advanced regional economic models The guidance addresses data needs, availability, and sources to support the analysis; agency staff capabilities; and audiences for information on productivity improvements This report will be useful to department of transportation staff and others responsible for project evaluation and presentation of evaluation results to decisionmakers

Recommended Bicycle Lane Widths for Various Roadway Characteristics

Abstract: Whether at the national, state, or local level, guidelines that have been developed for bicycle lane widths provide only general guidance on how bicycle lane widths should vary based on the conditions of the roadway. Thus, there was a need to conduct scientifically based research to develop more specific guidance on recommended bicycle lane widths for various roadway conditions. This report presents an analysis of the research and design guidance for bicycle lane widths on existing travel lane widths and parking lane widths. The research is based on a review of literature, the current state of practice, and a series of observational field studies. Temporary pavement markings were installed at several locations to delineate bicycle lanes of varying widths. The lateral positioning of both bicyclists and motorists was measured and used as surrogates to evaluate the safety effects of the allocation of roadway width between parking lanes, bike lanes, buffered spaces, and motor vehicle travel lanes. The data-collection sites included three midblock locations with on-street parking and two midblock locations where on-street parking was prohibited. The bicycle lane widths evaluated ranged from 3.5 to 6 ft. A supplemental grade study was also performed to evaluate lateral movement of bicyclists pedaling on a moderate upgrade. The report presents recommendations for bicycle lane widths for various roadway and traffic characteristics, including traffic volume, vehicle mix (i.e., percent trucks), lane width and/or total roadway width, and presence/absence of on-street parking. The conclusions are most applicable to urban and suburban roadways with level grade and a posted speed limit of 30 mph and should be used cautiously for the design of roadways with motor vehicle speeds outside of the range of 25 to 35 mph, and in particular for higher-speed roadways. This report will provide valuable guidance for traffic and design engineers in areas where bicycle lanes are being considered and implemented.

Factors Contributing to Median Encroachments and Cross-Median Crashes

Abstract: Previous studies of contributory factors associated with cross-median crashes have typically focused on median width and average daily traffic (ADT). A few studies have looked at the influence of geometry and cross-sectional elements. These studies did not explore many other design and operational factors that may contribute to cross-median crash frequency or severity (e.g., interchange ramps, interchange spacing, mixture of vehicle types, peak-period volumes, peak-period duration, land use, access control, driver workload, posted speed, or presence of speed transition zones). All median-related incidents begin with a median encroachment. Reducing median encroachments will reduce both cross-median crashes and fixed-object crashes in the median. Consequently, analyzing median encroachments should provide additional insight into the causes of cross-median crashes. There is also a knowledge gap regarding countermeasures appropriate for the various factors contributing to median encroachments and cross-median crashes. Although installing a barrier will greatly reduce cross-median crashes, it will also increase fixed-object crashes and the crash risk of maintenance personnel. Other countermeasures besides barriers exist, and knowing which ones effectively address the contributory factors on a highway will allow an engineer to develop a more effective design. This report identifies design and operational factors that contribute to the frequency and severity of median encroachments and cross-median crashes. It also identifies countermeasures for addressing those contributory factors. For this project, the research team reviewed the literature on median encroachments and cross-median crashes. Based on a survey of states, Canadian provinces, and turnpike/toll road authorities, the team compiled a list of design and operational factors likely to contribute to median encroachments and cross-median crashes. The research team then collected data to determine the relative contribution of each of the factors to median encroachments and cross-median crashes. Appendix D of the report provides recommended guidelines for reducing the frequency and severity of median-related crashes. This material is designed to be easily incorporated into a transportation agency’s design manual.

Performance-Based Analysis of Geometric Design of Highways and Streets

Abstract: For both new construction and reconstruction of highways and streets, stakeholders and decision makers increasingly want reasonable measures of the effect of geometric design decisions on the facility’s performance for all of its users. Although the expected performance of the facility is only one of the factors that must be considered in designing a highway or street, a better understanding of the expected performance should result in better decisions during the design process. This report presents ways to incorporate performance-based analysis into the project development process. This process framework begins with setting desired project multimodal outcomes and design controls. Geometric design decisions that can influence those outcomes are identified as well as analysis tools that can be used to estimate the impacts of those decisions. The report includes six project examples illustrating how this framework can be applied to actual projects. The report will be useful to geometric designers in making informed decisions about the tradeoffs inherent in design.

Design Guidance for Intersection Auxiliary Lanes

Abstract: A large proportion of crashes occur at intersections and auxiliary turn lanes are a key countermeasure for addressing such crashes. Auxiliary lanes can also be used to increase capacity and improve operations at an intersection. The design components of a traditional auxiliary turn lane consist of the length needed to store an appropriate number of waiting vehicles, a vehicle deceleration area, and the taper needed to develop the full lane width. Offset and indirect turn lanes and other types of auxiliary lanes (e.g., acceleration lanes) have similar components. The guidance and practice used throughout the United States for auxiliary lane designs and application vary by intersection location (e.g., rural or urban), traffic control (e.g., stop-control or signal-control), and lane type (e.g., right- or left-turn). AASHTO’s A Policy on Geometric Design of Highways and Streets (the Green Book) contains limited criteria for geometric design of auxiliary lanes at intersections. This report expands on that guidance, particularly regarding bypass lanes, channelized right-turn lanes, deceleration and taper length, design and capacity of multiple left-turn lanes, and alternative intersection designs. In National Cooperative Highway Research Program (NCHRP) Project 03-102, the Texas A&M Transportation Institute reviewed existing literature and ongoing research projects and identified issues meriting further study to validate, enhance, and expand current Green Book guidance. Field studies were conducted to assess the operation of double left-turn lanes and deceleration lanes. The research team then developed practical guidance for designers on auxiliary lanes, including recommendations for improving the Green Book. This report will be useful in updating agency design manuals and to those designing intersections.

Capacity Modeling Guidebook for Shared-Use Passenger and Freight Rail Operations

Abstract: This report provides technical guidance for state departments of transportation (DOTs) who are starting or expanding passenger rail service on privately-owned and shared-use rail corridors. The guidance is designed to aid in the DOTs’ understanding of the methods host railroads use to calibrate and apply capacity models to determine if adequate capacity exists to support new or increased passenger rail service or if infrastructure improvements may be necessary. A shared understanding of these methods will aid all parties—including state DOTs—in the negotiation of service outcome agreements. After an introductory chapter, the individual chapters present a synthesis of stakeholder input, analytical approaches to line capacity in shared-use corridors, best practices, and a discussion of recent and ongoing planning for the Chicago-Saint Louis high speed rail implementation on the Union Pacific Railroad and Canadian National Railway line. This report should be of immediate use to transportation professionals charged with the responsibility for planning passenger rail service and negotiating shared-corridor service agreements with host railroads.