Research Digest FORWARD ALL REQUESTS TO: The University of Texas at Austin Center for Transportation Research LIBRARY 1616 Guadalupe St.• Suite 4.202 • Austin • Texas • 78701 Phones: (512) 232-3126 and (512) 232-3138 Email: ctrlib@austin.utexas.edu
In this Issue: TxDOT Reports
Table of Contents Item 1. Mechanical Properties of Tire Bales for Highway Applications (CTR 5517-1) ...................................... 1 Item 2. Guidance for Feasibility Analysis of Candidate Sites: Handbook (CTR 5913-P1) ................................. 2 Item 3. Tour-Based Model Development for TxDOT (CTR 6210-2) ................................................................. 3 Item 4. Evaluation of TxDOT's J.A.C.K. Model for Revenue and Expenditure Projections (CTR 6395-CT-1).. 3 Item 5. Seal Coat Damage Evaluation Due to Superheavy Load Moves Based on a Mechanistic-Empirical Approach (TTI 5270-1) ......................................................................................................................................... 4 Item 6. Platoon Identification and Accommodation System Implementation in Brownwood and Caldwell, Texas (TTI 5507-01-1) .......................................................................................................................................... 4 Item 7. PIA Installation and User Guide: 2009 Update (TTI 5507-01-P3) .......................................................... 5 Item 8. Water Retention Techniques for Vegetation Establishment in TxDOT West Texas Districts (TTI 5748-1) ........................................................................................................................................................ 5 Item 9. Synthesis of Current Research on Permeable Friction Courses: Performance, Design, Construction, and Maintenance (TTI 5836-1) ............................................................................................................................. 6 Item 10. Guidelines for Spacing Between Freeway Ramps (TTI 5860-1) ........................................................... 6 Item 11. Roadside Sediment Control Device Evaluation Program: Technical Report (TTI 5948-1) ................... 7 Item 12. Evaluation of Barriers for Very High Speed Roadways (TTI 6071-2)................................................... 7 Item 13. New Generation Mix-Designs: Laboratory Testing and Construction of the APT Test Sections (TTI 6132-1).......................................................................................................................................................... 8 Item 14. Guidelines for Signal Operations at Intersections with Wide Medians (TTI 6176-1) ............................ 9 Item 15. Preserving Functionality/Asset Value of the State Highway System: Technical Report (TTI 6208-1) . 9 Item 16. Internal Trip Capture Estimator for Mixed-Use Developments (TTI 9032-01-1)................................ 10
Research and Technology Implementation Office May 2010
Research Digest Item 1 Mechanical Properties of Tire Bales for Highway Applications UNIVERSITY OF TEXAS AT AUSTIN. CENTER FOR TRANSPORTATION RESEARCH (CTR) CTR 5517-1 • 2009 Scrap tire bales are typically treated as discrete elements that consist of approximately one hundred (100) scrap tires compressed into a 4.5 foot by 5 foot by 2.5 foot block. The advantage of baling tires is that a volume reduction of approximately ten (10) is achieved, and handling bales is much simpler, and therefore cheaper, than whole tire or tire shreds. The use of tire bales in highway structures, however, requires that the mechanical properties of the tire bales are known. Determining these properties is vital to the proper design and construction of the tire bale structures. A literature review indicated the lack of material properties that are available for tire bales. A laboratory testing program was designed and implemented to determine the strength and compressibility properties of the bales required for design. Field testing to determine the unit weight and permeability of the tire bale mass was also conducted. Analytical studies and cost benefit analyses highlighting the benefits of using tire bales already assembled were also conducted for a series of tire bale case histories. The following document outlines all the work conducted as part of this, as well as previous, testing programs to determine the properties needed for design of tire bales structures, as well as economical aspects of reusing the tires as opposed to throwing them away. Full-text PDF of this report is available for free download from http://www.utexas.edu/research/ctr/pdf_reports/0_5517_1.pdf
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Research Digest Item 2 Guidance for Feasibility Analysis of Candidate Sites: Handbook UNIVERSITY OF TEXAS AT AUSTIN. CENTER FOR TRANSPORTATION RESEARCH (CTR) CTR 5913-P1 • 2009 The purpose of this handbook is to provide guidance in determining whether or not speed harmonization and peak period shoulder is feasible for a given site or set of sites. The content of this handbook is based on the analysis conducted for this project. Additional information regarding the topics presented in this handbook can be found in project report 0-5913-1, Speed Harmonization and Peak-Period Shoulder Use to Manage Urban Freeway Congestion. The guidance for conducting feasibility analyses, presented below, primarily integrates the cost benefit analysis framework and the operational and deployment strategy presented in Chapter 8 of the project report. The collective goal is to intelligently apply speed harmonization and peak period shoulder use as a combined traffic control strategy that delays the onset of severe congestion and increases throughput. Guidance for assessing the feasibility of speed harmonization and peak period shoulder use is organized into six analysis components. These are: 1) Identify candidate sites; 2) Construct and run microscopic and mesoscopic simulation; 3) Identify infrastructure improvements; 4) Develop an enforcement strategy and public education plan; 5) Apply cost benefit analysis framework; and 6) Consider potential qualitative impacts. Full-text PDF of this report is available for free download from http://www.utexas.edu/research/ctr/pdf_reports/0_5913_P1.pdf
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Research Digest Item 3 Tour-Based Model Development for TxDOT UNIVERSITY OF TEXAS AT AUSTIN. CENTER FOR TRANSPORTATION RESEARCH (CTR) CTR 6210-2 • 2009 The Texas Department of Transportation (TxDOT), in conjunction with the metropolitan planning organizations (MPOs) under its purview, oversees the travel demand model development and implementation for most of the urban areas in Texas. In these urban areas, a package of computer programs labeled as the "Texas Travel Demand Package" or the "Texas Package" is used as the decision making tool to forecast travel demand and support regional planning, project evaluation, and policy analysis efforts. The Texas Package currently adopts the widely used four-step trip-based urban travel demand modeling process, which was developed in the 1960s when the focus of transportation planning was to meet long-term mobility needs through the provision of additional transportation infrastructure supply. The trip-based model was intended to provide basic, aggregatelevel, long-term travel demand forecasts for long-range regional transportation plans and evaluation of major infrastructure investments. Over the past three decades, however, the supply-oriented focus of transportation planning has expanded to include the objective of evaluating a range of travel demand management strategies and policy measures to address rapidly growing transportation problems, including traffic congestion and air quality concerns. The travel demand management emphasis, combined with federal regulations, has placed additional information demands on the capabilities of travel demand models. As a result, new approaches have been developed to model and forecast travel demand. The new approaches include the tour-based modeling approach, which employs tours instead of trips as the unit of analysis. The tour-based approach enhances the ehavioral realism in modeling travel demand and the abilities of travel forecasting models in assessing transportation policies and evaluating alternative transportation investments. Hence, TxDOT is considering the implementation of tour-based modeling procedures. As a first step of a potential advanced model implementation, this proposed project evaluates the feasibility of, and documents the potential benefits from, a tour-based modeling process. It documents the steps to transition toward a tour-based framework, including an evaluation of data needs, software requirements, and software enhancements, ease of implementation and application, and staffing and related resource needs. Full-text PDF of this report is available for free download from http://www.utexas.edu/research/ctr/pdf_reports/0_6210_2.pdf
Item 4 Evaluation of TxDOT's J.A.C.K. Model for Revenue and Expenditure Projections UNIVERSITY OF TEXAS AT AUSTIN. CENTER FOR TRANSPORTATION RESEARCH (CTR) CTR 6395-CT-1 • 2009 This research report documents work conducted by the Center for Transportation (CTR) at The University of Texas at Austin in analyzing the Joint Analysis using the Combined Knowledge (J.A.C.K.) program. This program was developed by the Texas Department of Transportation (TxDOT) to make projections of revenues and expenditures. This research effort was to span from September 2008 to August 2009, but the bulk of the work was completed and presented by December 2008. J.A.C.K. was subsequently renamed TRENDS, but for consistency with the scope of work, the original name is used throughout this report. Full-text PDF of this report is available for free download from http://www.utexas.edu/research/ctr/pdf_reports/0_6395_CT_1.pdf
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Research Digest Item 5 Seal Coat Damage Evaluation Due to Superheavy Load Moves Based on a Mechanistic-Empirical Approach TEXAS A&M UNIVERSITY. TEXAS TRANSPORTATION INSTITUTE (TTI) TTI 5270-1 • 2010 The number of superheavy load (SHL) moves has increased drastically within the past 5 years in Texas. Along with the increasing SHL moves, the Texas Department of Transportation (TxDOT) has become increasingly aware of the rising concerns associated with fresh seal coat damage caused from SHL moves. Concerned about the effects of SHL moves on seal coat placed routes, TxDOT sponsored a research project with the Texas Transportation Institute to characterize critical factors related to the failure mechanism of seal coat, propose a mechanistic approach to evaluate failure potential, and develop a guideline for regulating SHL moves to mitigate further seal coat damages. This report describes research efforts and findings to propose a mechanistic approach to evaluate seal coat damage potential via charactering material properties playing a vital role in controlling seal coat behavior subject to SHL moves and validating the proposed mechanistic approach based on pilot field tests conducted in the Bryan and San Antonio Districts taking into account different levels of critical factors identified from this study. Moreover, the efforts were extended to establish a database on SHL routing information gathered from the TxDOT Construction Division from the pavement reviews conducted over the past 5 years in order to review the current guideline for SHLs. The project offered the first opportunity to provide a guideline for regulating SHL moves in order to preserve routes with fresh seal coats by delivering a tool that can be used to evaluate the route in a timely fashion before SHL moves occur. Full-text PDF of this report is available for free download from http://tti.tamu.edu/documents/0-5270-1.pdf
Item 6 Platoon Identification and Accommodation System Implementation in Brownwood and Caldwell, Texas TEXAS A&M UNIVERSITY. TEXAS TRANSPORTATION INSTITUTE (TTI) TTI 5507-01-1 • 2010 In Texas Department of Transportation (TxDOT) Project 0-5507, Texas Transportation Institute (TTI) researchers developed and filed-tested an enhanced version of a platoon identification and accommodation (PIA) system developed in an earlier research project. A key feature of the PIA-2 system developed in Project 0-5507 was its ability to detect and progress platoons in both arterial directions. The objective of this implementation project was to install the PIA-2 system at two additional locations in Texas. This report documents the work performed in this implementation project. Full-text PDF of this report is available for free download from http://tti.tamu.edu/documents/5-5507-01-1.pdf
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Research Digest Item 7 PIA Installation and User Guide: 2009 Update TEXAS A&M UNIVERSITY. TEXAS TRANSPORTATION INSTITUTE (TTI) TTI 5507-01-P3 • 2010 2009 Update to TTI 5507-01-P2: This research project enhanced a platoon identification and accommodation (PIA) system developed by Texas Transportation Institute (TTI) researchers in an earlier research project. The PIA system consists of off-the-shelf hardware and custom software for providing intelligent control at isolated traffic signals. This document contains detailed information required for installing and operating the enhanced version of the PIA system developed in TxDOT Project 0-5507. This document begins by providing a brief description of the PIA system, what it does, and where it could be installed. Then, the document provides detailed information about various system components, the approximated cost of each off-the-shelf hardware component and where to acquire it. Then, the document provides detailed instructions on how to install and configure needed software components, including the PIA software. Appendices provide additional information needed to configure communications links with traffic signal cabinets. Full-text PDF of this report is available for free download from http://tti.tamu.edu/documents/5-5507-01-P3.pdf
Item 8 Water Retention Techniques for Vegetation Establishment in TxDOT West Texas Districts TEXAS A&M UNIVERSITY. TEXAS TRANSPORTATION INSTITUTE (TTI) TTI 5748-1 • 2010 Water harvesting is the collection of runoff for its productive use and may aid in the germination and establishment of vegetation seeded in the roadside. This project is a synthesis study on the feasibility and implications of adapting water harvesting techniques to Texas roadsides in arid environments. The project uses a case-study approach via specific Texas Department of Transportation (TxDOT) roadway sites to investigate the potential application and impacts of adapting these techniques to roadside vegetation establishment and maintenance in a range of climate and soil conditions. The research seeks to develop alternative water harvesting techniques specifically adapted to the demanding environmental and safety requirements of the roadside. Recommendations for adoption are included along with guidelines, standard construction detail sheets, and specifications. A cost-benefit analysis for the various techniques and a recommendation for implementation of studies to field-verify the synthesis study is included in this report. Full-text PDF of this report is available for free download from http://tti.tamu.edu/documents/0-5748-1.pdf
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Research Digest Item 9 Synthesis of Current Research on Permeable Friction Courses: Performance, Design, Construction, and Maintenance TEXAS A&M UNIVERSITY. TEXAS TRANSPORTATION INSTITUTE (TTI) TTI 5836-1 • 2010 Over the past several years, the Texas Department of Transportation (TxDOT) adopted the use of porous or permeable friction course (PFC) mixtures as a thin asphalt pavement surface layer to provide safety and environmental benefits. This type of mixture is defined in TxDOT Specification Item 342 as a surface course of a compacted permeable mixture of aggregate, asphalt binder, and additives mixed hot in a mixing plant. Recent research addressed important design, construction, and maintenance issues associated with PFC, which has been increasingly employed by TxDOT. In order to complete the evaluation of this relatively new hot mix asphalt (HMA) concrete mixture type as a possible solution for improving pavement safety and reduction of pavement noise, performance will be tracked over time in this esearch project to assess benefits, cost, and changes in benefits. The main objective of this research project is to develop a database of PFC performance in terms of functionality (noise reduction effectiveness and permeability), durability (resistance to raveling and possibly rutting and cracking), and safety (skid resistance and accident history), in order to produce guidelines for design, construction, and maintenance of PFC mixtures. This report includes a comprehensive and focused review of research conducted since 2004 related to the mix design, performance (i.e., functionality, durability, and safety), construction, and maintenance of surface courses using PFC. Full-text PDF of this report is available for free download from http://tti.tamu.edu/documents/0-5836-1.pdf
Item 10 Guidelines for Spacing Between Freeway Ramps TEXAS A&M UNIVERSITY. TEXAS TRANSPORTATION INSTITUTE (TTI) TTI 5860-1 • 2010 Existing geometric design guidance related to interchange ramp spacing in the Texas Roadway Design Manual and the AASHTO's A Policy on Geometric Design of Highways and Streets (Green Book) is not speeddependent even though intuition indicates spacing and speed are related. Understanding the relationship between interchange ramp spacing, speed, and freeway operations is important, especially in developing potential design values for higher speeds (e.g., 85 to 100 mph). The objectives of this project were to: (a) investigate relationships between weaving length, speed, and overall vehicle operations on Texas freeways and (b) propose updates to current Texas Department of Transportation guidance on recommended distances between ramps. Within the research tasks several methods were utilized to assist in developing guidance on ramp spacing lengths. The methods or resources used to generate potential lengths included: guidance provided in Design Manual for Roads and Bridges published by the Highways Agency in England, minimum deceleration and acceleration length for freeway conditions, decision sight distance, sign spacing needs, NCHRP project 3-75 findings, findings from field studies at seven study sites, findings from simulation conducted as part of this research, and safety relationships identified in the literature. Suggested ramp spacings were developed for the entrance ramp to exit ramp and exit ramp to exit ramp conditions. Full-text PDF of this report is available for free download from http://tti.tamu.edu/documents/0-5860-1.pdf _____________________________________________________________________________________________
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Research Digest Item 11 Roadside Sediment Control Device Evaluation Program: Technical Report TEXAS A&M UNIVERSITY. TEXAS TRANSPORTATION INSTITUTE (TTI) TTI 5948-1 • 2010 One of the problems facing designers/engineers in maintaining regulatory compliance with the Environmental Protection Agency (EPA) and the Texas Commission on Environmental Quality (TCEQ) is the lack of quantifiable data to assist in selection effective sediment control best management practices (BMPs). Although the two principles of erosion and sediment control are often used interchangeably, they are two separate issues and require different BMPs for mitigation. Erosion control is any practice that protects the soil surface and minimizes soil particle detachment by water or wind. Sediment control is any practice that traps the soil particles after detachment and transport. Typically, effective sediment control is more difficult and expensive than erosion control. While erosion can never be completely, combining erosion and sediment control practices can significantly reduce sediment loss. To help ensure compliance, TxDOT successfully evaluates the performance of erosion control materials and maintains an Approved Product List (APL). This project will develop the formal protocol for a performance-based, sediment retention device testing program that will assist the designer/engineer in the selection of the most effective sediment control BMP. Full-text PDF of this report is available for free download from http://tti.tamu.edu/documents/0-5948-1.pdf
Item 12 Evaluation of Barriers for Very High Speed Roadways TEXAS A&M UNIVERSITY. TEXAS TRANSPORTATION INSTITUTE (TTI) TTI 6071-2 • 2010 As TxDOT plans for future expansion of the state's highway network, interest in higher design speeds has been expressed as a means of promoting faster and more efficient travel and movement of goods within the state. TxDOT funded project 0-6071 as part of a proactive consideration of safety on these highspeed facilities. This project began the process of developing roadside safety hardware suitable for use on high-speed highways. The impact conditions selected for the design, testing, and evaluation of this highspeed hardware include a speed of 85 mi/h and an angle of 25 degrees for barrier impacts. The design vehicles are those specified by the pending AASHTO Manual for Assessing Safety Hardware (MASH) and include a 5000-lb, -ton, 4-door pickup truck and a 2425-lb passenger car. After consideration of several barrier systems, two designs were selected for further evaluation through full-scale crash testing. These included an energy absorbing bridge rail concept and a modified wood post thrie beam guardrail. The results of the full-scale crash testing are presented and recommendations for future research are discussed. Full-text PDF of this report is available for free download from http://tti.tamu.edu/documents/0-6071-2.pdf
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Research Digest Item 13 New Generation Mix-Designs: Laboratory Testing and Construction of the APT Test Sections TEXAS A&M UNIVERSITY. TEXAS TRANSPORTATION INSTITUTE (TTI) TTI 6132-1 • 2010 Recent changes to the Texas HMA mix-design procedures such as adaption of the higher PG asphalt-binder grades and the Hamburg test have ensured that the mixes routinely used on the Texas highways are not prone to rutting. However, performance concerns have been raised about these mixes, which are now "drier", more difficult to compact, and more susceptible to cracking. This is particularly problematic with the dense-graded Type C and D mixes that are widely used throughout the State of Texas. Consequently, several new ideas are under consideration to either modify test procedures. Of primary focus in this research project is the comparative evaluation of the following three mix-design procedures and making recommendations thereof: (1) the modified volumetric mix-design procedure: (2) the Hamburg (rutting) and Overlay (cracking) test based balanced mixdesign procedure: and (3) a simplified balanced incorporates extensive literature review of the existing mixdesign procedures with a simpler alternative cracking test. The research methodology and scope of work incorporates extensive literature review of the existing mix-design procedures, laboratory testing, and field validation including accelerated pavement testing (APT) and performance monitoring. This interim report provides a preliminary overview of the mix-designs and laboratory test evaluations of three commonly used Texas mixes (namely Type B, Type C, and Type D) based on the Texas gyratory, volumetric, and balanced mix-design procedures. As well as conducting round-robin tests in six different Texas laboratories to quantify the Overlay test variability and repeatability, the laboratory tests also included comparative evaluation of various cracking tests such as the indirect tension, direct uniaxial tension, and semi-circular bending. HMA mix workability and compactability tests for quantifying the constructability aspects of the mixes were also conducted and are discussed in this report. Construction details of the APT test sections are also discussed in this interim report. Full-text PDF of this report is available for free download from http://tti.tamu.edu/documents/0-6132-1.pdf
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Research Digest Item 14 Guidelines for Signal Operations at Intersections with Wide Medians TEXAS A&M UNIVERSITY. TEXAS TRANSPORTATION INSTITUTE (TTI) TTI 6176-1 • 2010 The objective of this project is to evaluate the operations at signalized intersections with wide medians in order to improve safety and efficiency. Intersections with wide medians are characterized by two intersections and operate differently compared to a typical intersection. Space in the wide median between the two intersections can be used to store vehicles. However management of the storage space is critical to avoid queue backing up into the upstream intersection. There are no guidelines specific to operate such intersections. This results in agencies using their discretion to develop strategies to operate such intersections, resulting in inconsistent operations. Texas Transportation Institute researchers used VISSIM simulation model to evaluate numerous strategies that were either in use by TxDOT districts or were developed by the research team. These strategies were evaluated for various widths of medians, the number of lanes for the minor street in the median, and the presence of left-turn bays on the major street. The strategies were also evaluated for low, medium, and high volumes on the major street and on the minor street as well as different percentages of turning traffic. The research project produced recommended strategies for various volume and geometric conditions. Full-text PDF of this report is available for free download from http://tti.tamu.edu/documents/0-6176-1.pdf
Item 15 Preserving Functionality/Asset Value of the State Highway System: Technical Report TEXAS DEPARTMENT OF TRANSPORTATION (TXDOT) TEXAS A&M UNIVERSITY. TEXAS TRANSPORTATION INSTITUTE (TTI). TTI 6208-1 • 2010 Maintaining, preserving, and enhancing the functionality of state and local roadways of our transportation system is important because it maintains capacity and efficiency, reduces potential for congestion, maintains safety, reduces the need for further (or unplanned) improvements, and protects the value of our investments in both transportation infrastructure and adjacent land development. It is important that functionality be considered and in all stages of a highway's lifecycle. This report provides guidance on how to protect, preserve, and enhance highway functionality within the areas of planning and land development, operations and capacity, right of way, infrastructure and maintenance, and safety. Each of the five areas plays a part in establishing how well or poorly a highway may function and in meeting or preserving its intended function. The project includes case studies of the IH 10 Katy Freeway in Houston, SH 289 in Frisco and Plano, and SH 105 between the cities of Conroe and Montgomery, Texas. These case studies show how functionality changes over time and identifies opportunities to preserve or restore functionality. The report provides recommendations for how TxDOT, MPOs, local jurisdictions, and other transportation stakeholders and agencies can protect, preserve, and enhance the functionality of the state highway system in Texas. It represents report R1 of TxDOT research project 0-6208, Preserving Functionality/Asset Value of the State Highway System. Full-text PDF of this report is available for free download from http://tti.tamu.edu/documents/0-6208-1.pdf
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Research Digest Item 16 Internal Trip Capture Estimator for Mixed-Use Developments TEXAS A&M UNIVERSITY. TEXAS TRANSPORTATION INSTITUTE (TTI) TTI 9032-01-1 • 2010 This report describes a spreadsheet tool for estimating trip generation for mixed-use developments, accounting for internal trip capture. Internal trip capture is the portion of trips generated by a mixed-use development that both begin and end within the development. The importance of internal trip capture is that those trips satisfy a portion of the total development's trip generation and they do so without using the external road system. As a result, a mixed-use development that generates a given number of total trips creates less demand on the external road system than single-use developments generating the same number of trips. This report describes the spreadsheet estimator and how to use it. It describes the data behind the estimator as well as how those data are applied. The two Texas mixed-use developments from which most of the data were derived are also described. This report is supplemented by the ExcelŽ spreadsheet itself as well as task memoranda that document the survey data collected as part of this project Full-text PDF of this report is available for free download from http://tti.tamu.edu/documents/5-9032-01-1.pdf
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