Digest1004

Research Digest FORWARD ALL REQUESTS TO: The University of Texas at Austin Center for Transportation Research LIBRARY 1616 Guadalupe • Austin • Texas • 78701 Phones: (512) 232-3126 and (512) 232-3138 • Fax: (512) 232-3088 Email: ctrlib@austin.utexas.edu

In this Issue: TxDOT Reports

Table of Contents Item 1. Pilot Implementation of New Test Procedures for Curing in Concrete Pavements (CTR 5106-01-1) ........................................................................................................................................... 1 Item 2. Estimated vs. Forecasted Toll Usage: A Case Study Review (CTR 6044-1) ................................... 2 Item 3. Tour-Based Model Development for TxDOT (CTR 6210-1) .......................................................... 2 Item 4. Special Studies for TxDOT Administration in FY 2009 (CTR 6581-CT-1) ................................... 3 Item 5. Full-Scale Controlled Tests of Wind Loads on Traffic Signal Structures (TechMRT 4586-3) ........ 3 Item 6. Tests of HMA Overlays Using Geosynthetics to Reduce Reflection Cracking (TTI 1777-3) ......... 4 Item 7. Development of Safety Performance Monitoring Procedures (TTI 4703-7).................................... 4 Item 8. Mobility Monitoring in Your Community -- Interactive Workshop (TTI 5571-01-P1) .................. 5 Item 9. Improving Accuracy in Household and External Travel Surveys (TTI 5711-1) .............................. 5 Item 10. Guidelines and Recommendations for Household and External Travel Surveys (TTI 5711-P1) .. 6 Item 11. Quantifying the Effects of Network Improvement Actions on the Value of New and Existing Toll Road Projects (TTI 5881-1) ................................................................................................................... 6 Item 12. Driver Workload at Higher Speeds (TTI 5911-1) .......................................................................... 7 Item 13. Development of a Video Over IP Guidebook (TTI 5942-1) .......................................................... 7 Item 14. Improved Intersection Operations During Detector Failures (TTI 6029-1) ................................... 8 Item 15. RAP Stockpile Management and Processing in Texas: State of the Practice and Proposed Guidelines (TTI 6092-1) ............................................................................................................................... 9 Item 16. Expert System for Pavement Remediation Strategies (ExSPRS) User's Manual (UTEP 5430-P3) ........................................................................................................................................... 9 Item 17. Accelerated Stabilization Design of Subgrade Soils (UTEP 5569-1) .......................................... 10 Item 18. Design Manual and Test Protocols to Accelerate Mix Design of Stabilized Subgrades (UTEP 5569-P1 & UTEP 5569-P2) ........................................................................................................... 10

Research and Technology Implementation Office April 2010

Research Digest Item 1 Pilot Implementation of New Test Procedures for Curing in Concrete Pavements UNIVERSITY OF TEXAS AT AUSTIN. CENTER FOR TRANSPORTATION RESEARCH (CTR) CTR 5106-01-1 • 2009 Curing of concrete has substantial effects on the performance of Portland cement concrete (PCC) pavement.

Curing effectiveness depends on the quality of the curing materials, time of curing compound application in relation to evaporation, and the amount and uniformity of the curing compound applications. The Texas Department of Transportation (TxDOT) developed and maintains a quality monitoring (QM) program for curing compounds to ensure that curing compounds used in TxDOT projects meet the minimum requirements. The timing of curing compound application as required in the specifications is well adhered. On the other hand, the uniformity and the amount of curing compounds applied are not monitored as well as they should be, primarily due to the lack of simple and proper methods for verifying their compliance with the specification requirements.

To ensure good quality of curing in TxDOT paving projects, there is a need for simple and easy-to-use compliance testing. TxDOT Research Project 0-5106 evaluated and identified potential compliance testing for curing compound application rate and uniformity. Speed control of the curing machine was the basis for the compliance testing utilizing non-contact Doppler radar speed sensor and wireless data logger system. This project evaluated the feasibility of implementing this compliance testing in TxDOT construction projects. The findings include (1) speed control of the curing machine could be the most practical and simple method for compliance testing, (2) the non-contact Doppler radar speed sensor and the wireless data logger showed fairly good performance and can be an effective and practical curing compliance testing system, and (3) as the wind speed increases, the loss of curing compound tends to increase nearly proportionally. Since the proposed system is more complicated than the system than the current practice, a simpler approach was developed and recommended for quick implementation.

Full-text PDF of this report is available for free download from http://www.utexas.edu/research/ctr/pdf_reports/5_5106_01_1.pdf

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Research Digest Item 2 Estimated vs. Forecasted Toll Usage: A Case Study Review UNIVERSITY OF TEXAS AT AUSTIN. CENTER FOR TRANSPORTATION RESEARCH (CTR) CTR 6044-1 • 2008 Reliable T&R forecasts are critical to the success of toll proposals. However, a number of studies by the bond rating agencies—specifically Standard & Poor’s (S&P)—have shown that a majority of toll roads failed to meet revenue expectations in their first full year of operation. These studies alluded to the existence of an optimism bias in T&R forecasts, with an over-estimation of traffic by 20-30 percent in the first five years of operation.

This uncertainty contributes to increased risks about the feasibility of toll roads, requirements for escrow accounts of up to 30 percent of the amount borrowed, and thus high interest payments (and ultimately higher costs to the users) to compensate investors for higher risks. The objective of this research study was to expand upon the analysis conducted by the bond rating agencies. The research focused on toll road case studies that have been operational for varying lengths of time in areas with similar demographic and transportation characteristics as Central Texas. Special care was taken to ensure the inclusion of more mature systems. This research report (a) summarizes the analysis done by S&P, J.P. Morgan, and a recent National Cooperative Highway Research Program Synthesis study on toll road demand and revenue forecasting, (b) details the researchers’ understanding of the general T&R approach used by the industry, (c) documents the research approach and summarizes the salient case study findings, (d) lists a number of areas that requires an improved understanding to enhance the reliability of T&R forecasts of toll roads, (e) provides specific recommendations to address some of the concerns about data and data sourcing, the identification of key variables and how they are considered in the T&R forecasts, the limitations of the modeling methods used, and the sensitivity of T&R forecasts to changes in key variables, and (f) concludes with a brief description of the next year’s research activities.

Full-text PDF of this report is available for free download from http://www.utexas.edu/research/ctr/pdf_reports/0_6044_1.pdf

Item 3 Tour-Based Model Development for TxDOT UNIVERSITY OF TEXAS AT AUSTIN. CENTER FOR TRANSPORTATION RESEARCH (CTR) CTR 6210-1 • 2009 Travel demand modeling, in recent years, has seen a paradigm shift with an emphasis on analyzing travel at the individual level rather than using direct statistical projections of aggregate travel demand as in the trip-based approach. Specifically, several metropolitan planning organizations (MPO) in the U.S are developing and implementing advanced travel demand models that are based on a behaviorally more realistic representation of demand for travel. In addition, a number of planning agencies are considering the transition toward advanced travel demand modeling, TxDOT being one of them. Toward this end, this report provides the details of implementing a tour-based travel demand model system. Specifically, the implementation steps are provided for a tour-based model system (with no recognition of the interactions among tours). This includes discussion on data assembly and data preparation, model estimation and calibration (validation), trip assignment output validation, and software recommendations and budgetary considerations.

Full-text PDF of this report is available for free download from http://www.utexas.edu/research/ctr/pdf_reports/0_6210_1.pdf

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Research Digest Item 4 Special Studies for TxDOT Administration in FY 2009 UNIVERSITY OF TEXAS AT AUSTIN. CENTER FOR TRANSPORTATION RESEARCH (CTR) CTR 6581-CT-1 • 2009 This research project was established by TxDOT's Research and Technology Implementation Office to address special studies required by the department's Administration during FY 2009. Five short-term, quick turnaround tasks were completed and are documented.

Full-text PDF of this report is available for free download from http://www.utexas.edu/research/ctr/pdf_reports/0_6581_CT_1.pdf

Item 5 Full-Scale Controlled Tests of Wind Loads on Traffic Signal Structures TEXAS TECH UNIVERSITY, (TECHMRT) TechMRT 4586-3 • 2008 The wind-induced vibrations of the mast arm of cantilever traffic signal structures can lead to the fatigue failure of these structures. For this project, both full-scale and wind tunnel tests were conducted to study the behavior of the structures. Results of these experiments indicated that when the signals have backplates, vortex shedding can cause large-amplitude vibrations that may lead to fatigue failure. These results contradict what has been generally accepted by other researchers: that galloping is the main cause for the fatigue inducing vibrations and that vortex shedding is of no relevance in this type of structure.

Full-text PDF of this report is available for free download from http://www.depts.ttu.edu/techmrtweb/Reports/Complete%20Reports/0-4586-3_final.pdf

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Research Digest Item 6 Tests of HMA Overlays Using Geosynthetics to Reduce Reflection Cracking TEXAS A&M UNIVERSITY. TEXAS TRANSPORTATION INSTITUTE (TTI) TTI 1777-3 • 2009 The primary objective of this field phase of the research project was to evaluate geosynthetic products placed under or within hot mix asphalt overlays to reduce the severity or delay the appearance of reflection cracks and to calibrate and validate FPS-19 Design Check. Multiple end-to-end test pavements incorporating geosynthetic products (fabrics, grids, and composites) and including control sections were constructed in three different regions of Texas (Amarillo, Waco, and Pharr Districts) with widely different climates and geological characteristics. Performance of these test pavements has been monitored for five to six years, depending on the date of construction. The oldest test pavements (Pharr) are exhibiting essentially no cracking. The Amarillo and Waco test pavements are exhibiting a fair amount of low severity and a very small amount of mediumseverity reflective cracking. Based on measured cracks in the original pavement before overlaying, the percentage of reflective cracking in each test section was calculated and plotted with time of pavement in service. Calibration of FPS-19 Design Check could not be accomplished due to the absence of sufficient amount of cracks with medium-severity level. Instead, using the field data, relative life ratio of test sections was projected. Field specimens obtained from these test pavements were tested using the large overlay tester. Field monitoring revealed that some geosynthetic products are effective in delaying reflective cracking. They were relatively more effective in the Waco test pavement (concrete in mild climate) than the Amarillo test pavement (flexible in harsh climate).

Full-text PDF of this report is available for free download from http://tti.tamu.edu/documents/0-1777-3.pdf

Item 7 Development of Safety Performance Monitoring Procedures TEXAS A&M UNIVERSITY. TEXAS TRANSPORTATION INSTITUTE (TTI) TTI 4703-7 • 2010 Highway safety is an ongoing concern to the Texas Department of Transportation (TxDOT). As part of its proactive commitment to improving highway safety, TxDOT is moving toward including quantitative safety analyses earlier in the project development process. The objectives of this research project are: (1) the development of safety design guidelines and evaluation tools to be used by TxDOT designers, and (2) the production of a plan for the incorporation of these guidelines and tools in the planning and design stages of the project development process. This document summarizes the research that was conducted and the products that were developed during this six-year research project. It also describes a plan to incorporate safety design guidelines and evaluation tools into the project development process. It is intended for use by engineers responsible for the planning and design of streets and highways.

Full-text PDF of this report is available for free download from http://tti.tamu.edu/documents/0-4703-7.pdf

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Research Digest Item 8 Mobility Monitoring in Your Community -- Interactive Workshop TEXAS A&M UNIVERSITY. TEXAS TRANSPORTATION INSTITUTE (TTI) TTI 5571-01-P1 • 2010 Participant's Workbook & Instructor's Guide. Workshop objectives include: describe causes of congestion in SMSCs; list and describe six steps of the mobility monitoring framework; identify a range of mobility performance measures and their application; describe the development and application of performance targets; develop a mobility monitoring plan; calculate basic mobility performance measures; describe reader-friendly communication techniques; describe benefits of improving monitoring process; describe contents and application of the Guidebook.

Full-text PDF of this report is available for free download from http://tti.tamu.edu/documents/5-5571-01-P1.pdf

Item 9 Improving Accuracy in Household and External Travel Surveys TEXAS A&M UNIVERSITY. TEXAS TRANSPORTATION INSTITUTE (TTI) TTI 5711-1 • 2010 The Texas Department of Transportation has a comprehensive on-going travel survey program. This research examines areas within two select travel surveys concerning quality control issues involved in data collection and sampling error in the data caused by various assumptions, survey methods, and issues such as non-response.

Quality control issues, sampling errors, and non-response in external and household travel surveys conducted in Texas are identified, examined, and evaluated. The impact of these issues is quantified and evaluated relative to the use of the data in travel demand models. The state-of-the-practice in these types of surveys relative to quality control during and after the surveys are conducted and how sampling errors and non-response are treated (or corrected) in the survey analysis are reviewed and documented. The results are assessed to formulate a set of recommendations for incorporating into survey designs for the travel survey program.

Full-text PDF of this report is available for free download from http://tti.tamu.edu/documents/0-5711-1.pdf

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Research Digest Item 10 Guidelines and Recommendations for Household and External Travel Surveys TEXAS A&M UNIVERSITY. TEXAS TRANSPORTATION INSTITUTE (TTI) TTI 5711-P1 • 2010 The Texas Department of Transportation has a comprehensive ongoing travel survey program. Research under RMC 0-5711 examined areas within two select travel surveys concerning quality control issues involved in data collection and sampling error in the data caused by various assumptions, survey methods, and issues such as nonresponse. Quality control issues, sampling errors, and non-response in external and household travel surveys conducted in Texas were identified, examined, and evaluated. This report presents an assessment of various quality control issues for household and external surveys in Texas. Much of it is based on the research documented in RMC 0-5711-R1. This report extends those findings and includes documentation on the individual data element checks performed on the data from household and external surveys conducted in Texas.

A set of guidelines and recommendations are presented to maintain and improve quality control for household and external surveys in Texas.

Full-text PDF of this report is available for free download from http://tti.tamu.edu/documents/0-5711-P1.pdf

Item 11 Quantifying the Effects of Network Improvement Actions on the Value of New and Existing Toll Road Projects TEXAS A&M UNIVERSITY. TEXAS TRANSPORTATION INSTITUTE (TTI) TTI 5881-1 • 2010 Development, delivery, and operation of public infrastructure are becoming increasingly dependent on participation of the private sector. While revenue generating projects, such as toll roads, were traditionally developed and funded from the public sources, in recent years, as the public demand for new projects have exceeded the ability of the public sector to deliver them, the private investors have started to fulfill the gap between the needed and the available infrastructure. The objective of this research was to develop a networkbased method that allows an assessment of the effect of the public sector's decisions regarding network improvements on the financial value of toll road projects.

Accompanying CD, Webinar: Workshop Training Materials, available upon request from the Center for Transportation Research Library.

Full-text PDF of this report is available for free download from http://tti.tamu.edu/documents/0-5881-1.pdf

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Research Digest Item 12 Driver Workload at Higher Speeds TEXAS A&M UNIVERSITY. TEXAS TRANSPORTATION INSTITUTE (TTI) TTI 5911-1 • 2010 The goal of this Texas Department of Transportation project was to gain a better understanding of driver performance at high speeds. Specific efforts included the following studies: The Closed-Course Pilot Study consisted of observing and recording the activities and actions of a series of drivers following a lead vehicle going either 60 or 85 mph. The Open-Road Pilot Study recorded participants driving between Odessa and Pecos, Texas, within 70- and 80-mph sections. The Simulator Pilot Study determined driver reactions to a looming vehicle (both passenger car and large truck) and also generated directions for how to conduct the Phase II simulator study. The Simulator Phase II Study collected brake reaction to a vehicle looming in the driver's view for 50 participants. Conditions varied included initial speed, lead vehicle type, lead vehicle deceleration rate, and workload level. The Following Distance Study used data from traffic counters to identify speed and axle gap data on freeways with 60-, 70-, and 80-mph posted speed limits.

The Gaps at Passing Study measured gaps during passing maneuvers for daylight conditions on freeway sections.

When responding to a vehicle slowing in their lane, drivers in the Simulator Phase II Study at the 85-mph speed had a reaction time that was statistically longer than that of drivers at the 60-mph speed. In the simulator, onroad, and test track studies where researchers directly measured driver performance, performance declined when a driver was multitasking at the higher speed. The traffic counter data showed that axle clearance distance was larger for the 80-mph freeway sites as compared to the 60- and 70-mph speed limit sites, both statistically and practically. The Gaps at Passing Study found a different result; drivers used similar passing gap distances on both 70- and 80-mph sections.

Full-text PDF of this report is available for free download from http://tti.tamu.edu/documents/0-5911-1.pdf

Item 13 Development of a Video Over IP Guidebook TEXAS A&M UNIVERSITY. TEXAS TRANSPORTATION INSTITUTE (TTI) TTI 5942-1 • 2009 Texas Department of Transportation (TxDOT) engineers are responsible for the design, evaluation, and implementation of video solutions across the entire state. These installations occur with vast differences in requirements, expectations, and constraints. Because the systems require extensive interoperability to other systems, agencies, and deployments, a systems engineering process (SEP) is employed to develop a consistent and structured approach to the development of concepts, needs, requirements, design, testing, and on-going operations. This report details the development of a guidebook and supplemental CD-ROM for TxDOT engineers to understand, assess, and deploy digital video solutions.

Full-text PDF of this report is available for free download from http://tti.tamu.edu/documents/0-5942-1.pdf

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Research Digest Item 14 Improved Intersection Operations During Detector Failures TEXAS A&M UNIVERSITY. TEXAS TRANSPORTATION INSTITUTE (TTI) TTI 6029-1 • 2010 The objective of this project was to develop three modules that would improve the efficiency of intersection operations at isolated signalized intersections. The motivation for these modules was to use the existing detectors more efficiently. This would in turn reduce the number of detectors required at the intersection and also improve operations in case of detector failures. The adaptive variable initial module (Module 1) can improve the typical variable initial feature available in most signal controllers by factoring the turning movements at the intersections in real time along with queue distribution, and activity on driveways between the detectors and stop bar. The detector failure module (Module 2) develops a rolling database of phase utilizations of all phases at the intersections. The module uses this database to determine the appropriate phase time when a detector failure is identified. The variable detector module (Module 3) monitors the phase utilizations on the major-street phase and the volume on the right-turn and left-turn detectors to vary the delay programmed on detectors to further improve the intersection operations. Researchers evaluated Module 1 and Module 2 and found them improving the intersection operations. However, initial implementations of Module 3 showed limited benefits and only under very rare conditions. Thus, researchers did not develop Module 3 further. Modules 1 and 2 require data that are easily available within the controller and can be incorporated into the signal controller firmware.

Full-text PDF of this report is available for free download from http://tti.tamu.edu/documents/0-6029-1.pdf

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Research Digest Item 15 RAP Stockpile Management and Processing in Texas: State of the Practice and Proposed Guidelines TEXAS A&M UNIVERSITY. TEXAS TRANSPORTATION INSTITUTE (TTI) TTI 6092-1 • 2010 In addition to conserving energy and protecting the environment, the use of reclaimed asphalt pavement (RAP) can significantly reduce the increasing cost of asphalt mixes. However, one of the key problems with RAP mixes is its variability, which is the main reason why many states including Texas Department of Transportation (TxDOT) limit the use of RAP. In most circumstances, RAP variability is closely related to RAP stockpiles management and RAP processing. This report first documents the state of the practice of RAP stockpile management and RAP processing in Texas. In contrast to the RAP stockpiles owned by TxDOT, most contractors currently combine materials from different RAP sources and sometimes waste into a single pile and then process it into a usable material by crushing and/or fractionation. During the first year of this study it was found that the contractors visited are doing a good job of managing the processed RAP stockpiles. To quantify the RAP variability, samples were collected from several stockpiles and evaluated using asphalt ignition oven test. The results showed that both TxDOT's and contractors' RAP materials, in terms of aggregate gradation and asphalt content, are consistent and slightly better than those reported at the national level. However, one concern raised during the visits is with mixing multiple source RAP stockpiles before crushing or fractionation. RAP stockpiles are often processed or dug from a single angle or sequentially and then directly fed into a crushing or fractionating machine. If there is no further blending after crushing or fractionation, the processed RAP may still be multiple-source. In this report guidelines are proposed to address this and other issues related to stockpiles management and RAP processing. The key points are to 1) eliminate contamination of RAP stockpiles, 2) keep RAP stockpiles separate as possible, 3) blend thoroughly before processing or fractionating the multiple-source RAP stockpiles, 4) avoid over-processing (avoid generating too much fines passing # 200 sieve size), 5) use good practices when storing the processed RAP (such as using paved, sloped storage area), and 6) characterize and number the processed RAP stockpiles. To better control the RAP variability, both good stockpile management practices and RAP processing techniques described in this report should be followed.

Full-text PDF of this report is available for free download from http://tti.tamu.edu/documents/0-6092-1.pdf

Item 16 Expert System for Pavement Remediation Strategies (ExSPRS) User's Manual UNIVERSITY OF TEXAS AT EL PASO (UTEP) UTEP 5430-P3 • 2008 This research project was focused on low-volume roads over expansive clayey soils in Texas. The intent of this research project was to cultivate the vital features of strategies for improving low-volume flexible pavement design and thus improving the overall low-volume road performance.

Full-text PDF of this report is available for free download from http://ctis.utep.edu/publications/Reports/18TX0-5430%20final%20P3%20ExSPRS%20Manual.pdf

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Research Digest Item 17 Accelerated Stabilization Design of Subgrade Soils UNIVERSITY OF TEXAS AT EL PASO. CENTER FOR TRANSPORTATION INFRASTRUCTURE SYSTEMS UTEP 5569-1 • 2010 Chemical stabilizers are commonly used to improve the performance of problematic soils. Lime, cement, and fly ash are typically used for this purpose. To achieve effective soil stabilization, type and concentration of the stabilizer are usually calculated based on the plasticity and gradation of the material. To archive the mix design, the optimum stabilizer content is usually based on experience or following time-consuming specifications. New accelerated testing methods are proposed that minimize the time required for soil specimen preparation, curing, and moisture conditioning to complete the design process. Proposed methods were compared to current specifications. A curing time of 2 days and a back-pressure method to complete moisture conditioning are recommended to complete the mix design in 3 days.

In addition, a more rigorous soil classification which considers the soil mineralogy is included. For that matter,s simple chemical methods to determine the mineralogy of the soil fines are included. Cation Exchange Capacity, Specific Surface Area and Total Potassium could be used to substitute methods such as X-ray Diffraction and Scanning Electron Microscope.

Durability and permanency studies on the treated and untreated soils were also evaluated to address the permanency and leachability of the chemical stabilization associated with rainfall infiltration and to simulate seasonal changes. Other important issues that are evaluated are adequate mixing and curing, adequate density and moisture, adequate short-term and long term strength and stiffness, and proper construction.

Full-text PDF of this report is available for free download from http://ctis.utep.edu/publications/Reports/3Report%200-5569%20Final.pdf

Item 18 Design Manual and Test Protocols to Accelerate Mix Design of Stabilized Subgrades UNIVERSITY OF TEXAS AT EL PASO. CENTER FOR TRANSPORTATION INFRASTRUCTURE SYSTEMS UTEP 5569-P1 UTEP 5569-P2 • 2009 This document establishes recommended evaluation criteria to select stabilization type and content, methods of evaluating the effectiveness of stabilization, and methods for moisture conditioning of samples to accelerate the mix design process and to evaluate the effectiveness of stabilization. This revised procedure is an adaptation of the current guidelines for subgrade stabilization, with the addition of chemical analysis of the soil fines to identify clay mineralogy, accelerated curing and moisture conditioning to minimize to time to achieve the mix design and wetting-drying cycles as means of durability indicators. In addition a static compaction method for preparing fine-grained soil specimens is recommended.

Full-text PDF of this report is available for free download from http://ctis.utep.edu/publications/Reports/17Project%2005569%20Products%20P1%20and%20P2%20revised_Aug17%20PUB2.pdf

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