For this project, an optimization scheme was developed to locate Road Weather Information System (RWIS) stations along the Interstate Highway 35 (IH-35) corridor for the Austin TxDOT district. In order to do this, eight major roadways in the three counties, Williamson, Travis, and Hays, that IH-35 passes through were chosen for analysis. Four north-south highways were selected, IH-35, SH-130, SL-1, and US-183, and four east-west highways were selected, SH-45, US-79, US-290, and SH-71. Crash Record Information System (CRIS) crash data was used to determine crashes that happened along these routes between 2006 and 2011 during inclement weather conditions. Routes were broken up into segments of equal lengths and crash rates were determined using TXDOT AADT information. These crash rates were calculated over a smoothing distance larger than the segment distances to provide more consistent rates and optimal locations were determined using a maximization algorithm based on the crash rate for these segments and their distance away from the sensor locations. Applying different segment lengths, smoothing distances, and crash data in analysis yielded varying optimal locations that were analyzed based on coverage area within the three county analysis region based on a 10 mile radius of coverage for each station. / text

The thesis investigates potential methods of linking transportation planning in Texas, principally long range planning, with the environmental clearance process required of the National Environmental Policy Act (NEPA). The purpose of the research is to achieve time and monetary savings by streamlining the NEPA process. These savings result principally by reducing duplicative efforts performed during transportation planning and the NEPA process. To achieve this goal, the thesis reviews the effectiveness of practices and efforts done in Texas and around the country designed to encourage planning documentation that supports the NEPA process. The thesis then assesses the challenges involved with implementing these practices in Texas and makes a series of recommendations designed to be implemented by various agencies in Texas that would provide linkages between transportation planning and the NEPA process. / text

The purpose of this study was to improve flexible base course performance within the state of Texas while reducing TxDOT’s testing burden. The focus of this study was to revise the current specification with the intent of providing a “performance related” specification while optimizing sample sizes and testing frequencies based on material variability. A literature review yielded information on base course variability within and outside the state of Texas, and on what tests other states, and Canada, are currently using to characterize flexible base performance. A sampling and testing program was conducted at Texas A&M University to define current variability information, and to conduct performance related tests including resilient modulus and permanent deformation. In addition to these data being more current, they are more representative of short-term variability than data obtained from the literature. This “short-term” variability is considered more realistic for what typically occurs during construction operations. A statistical sensitivity analysis (based on the 80th percentile standard deviation) of these data was conducted to determine minimum sample sizes for contractors to qualify for the proposed quality monitoring program (QMP). The required sample sizes for contractors to qualify for the QMP are 20 for gradation, compressive strength, and moisture-density tests, 15 for Atterberg Limits, and 10 for Web Ball Mill. These sample sizes are based on a minimum 25,000 ton stockpile, or “lot”. After qualifying for the program, if contractors can prove their variability is better than the 80th percentile, they can reduce their testing frequencies. The sample size for TxDOT’s verification testing is 5 samples per lot and will remain at that number regardless of reduced variability. Once qualified for the QMP, a contractor may continue to send material to TxDOT projects until a failing sample disqualifies the contractor from the program. TxDOT does not currently require washed gradations for flexible base. Dry and washed sieve analyses were performed during this study to investigate the need for washed gradations. Statistical comparisons of these data yielded strong evidence that TxDOT should always use a washed method. Significant differences between the washed and dry method were determined for the percentage of material passing the No. 40 and No. 200 sieves. Since TxDOT already specifies limits on the fraction of material passing the No. 40 sieve, and since this study yielded evidence of that size fraction having a relationship with resilient modulus (performance), it would be beneficial to use a washed sieve analysis and therefore obtain a more accurate reading for that specification. Furthermore, it is suggested the TxDOT requires contractors to have “target” test values, and to place 90 percent within limits (90PWL) bands around those target values to control material variability.

The purpose of this study is to assist TxDOT engineers in the field of traffic control planning. This is to be done via the creation of a Geographic Information System (GIS) based tool. By bringing together information about TxDOT’s on-system roadways’ geographical locations, traffic demands, and capacities, one aggregate database has been established. Using the tools of GIS, Microsoft Excel, Microsoft Access, and VBA programming, a static clickable interface has been constructed. It enables users to access properties for any selected roadway link they desire. Expansion of the product to ArcIMS is ongoing to allow easy access for end users via the internet. / text

The coefficient of thermal expansion (CTE) is one of the major factors responsible for distresses in concrete pavements and structures. Continuously reinforced concrete pavements (CRCPs) in particular are highly susceptible to distresses caused by high CTE in concrete. CRCP is a popular choice across the U.S. and around the world for its long service life and minimal maintenance requirements. CRCP has been built in more than 35 states in the U.S., including Texas. In order to prevent CRCP distresses, the Texas Department of Transportation (TxDOT) has limited the CTE of CRCP concrete to a maximum of 5.5 x10-6 strain/oF (9.9 x10-6 strain/oC). Coarse aggregate sources that produce concrete with CTE higher than the allowable limit are no longer accepted in the TxDOT CRCP projects. Moreover, CTE is an important input in the Mechanistic-Empirical Pavement Design Guide (MEPDG). Small deviations in input CTE can affect the pavement thickness significantly in MEPDG designs. Therefore, accurate determination of concrete CTE is important, as it allows for enhanced concrete structure and pavement design as well as accurate screening of CRCP coarse aggregates. Moreover, optimizing the CTE of concrete according to a structure’s needs can reduce that structure’s cracking potential. This will result in significant savings in repair and rehabilitation costs and will improve the durability and longevity of concrete structures. This study found that the CTEs determined from saturated concrete samples were affected by the internal water pressure. As a result, the TxDOT method yielded higher values than did the American Association of State Highway and Transportation Officials (AASHTO) method. To further investigate the effect of internal water pressure, an analytical model was developed based on the poroelastic phenomenon of concrete. According to the model, porosity, permeability, and the rate of temperature change are the major factors that influence the internal water pressure development. Increasing the permeability of concrete can reduce the internal water pressure development and can thus improve the consistency of measured CTE values. Preconditioning concrete samples by subjecting them to several heating and cooling cycles prior to CTE testing and reducing the rate of temperature change improved the consistency of the CTE test results. Concrete CTE can be reduced by blending low-CTE aggregates with high-CTE aggregates and reducing the cement paste volume. Based on these findings, a concrete CTE optimization technique was developed that provides guidelines for the selection of concrete constituents to achieve target concrete CTE. A concrete proportioning technique was also developed to meet the need for CTE optimization. This concrete proportioning technique can use aggregate from any sources, irrespective of gradation, shape, and texture. The proposed technique has the potential to reduce the cement requirement without sacrificing performance and provides guidelines for multiple coarse and fine aggregate blends. / text

Efficient, reliable, and safe freight transportation is critical to the economic prosperity of any region. In the U.S., the dramatic increase in freight volumes has resulted in the growing disparity between demand and capacity. Thus, freight planning is needed to ensure a seamless and effective Texas's transportation system. A clear understanding on the performance of Texas's transportation system, as perceived by the private sector is a critical component in the development of such planning efforts. Against this background, the objective of this research study was to start engaging Texas's shippers and freight stakeholders in a dialogue to provide insight into the adequacy of Texas's transportation system in serving business needs, and any improvements deemed necessary to better serve Texas businesses. The emphases of this study were on the freight concerns and needs, freight policies and strategies, and freight performance measures as expressed by Texas freight stakeholders. / text

Many Departments of Transportation (DOTs), including Texas Department of Transportation (TxDOT), have been challenged by inadequate funding from traditional federal and state fuel taxes, increasing construction cost, aging highway system, traffic congestions, and recent natural disasters, compromising their primary mission to provide safe vehicle transportation routes with adequate capacity. Furthermore, environmental awareness and sustainability concept have strengthened and sparked debates in Congress, culminating with several regulatory policies that affect, inclusively, transportation projects. This scenario has prompted DOTs to pursue innovative ways to reduce maintenance cost (at minimum) and generate revenue (at maximum) exploiting their assets, and to meet the new regulations. Likewise, the Center of Transportation Research at The University of Texas at Austin undertook a comprehensive research study to identify and determine when, where, and under what circumstances TxDOT should pursue the implementation of which Value Extraction Application (VEA), and how to effectively recognize and involve key stakeholders. As a result, 11 VEAs were identified. In addition, a methodological framework – embedding a multi-attribute criteria analysis matrix as the decision making method - was devised to guide TxDOT throughout the process of identifying, evaluating, comparing, and selecting the most appropriate VEA while a list of stakeholders associated with each VEA and a stakeholder analysis framework was provided to help TxDOT to identify and reach out key stakeholders. / text

An investigation into the load-settlement behavior of two drilled shafts, founded in shale, is presented. The motivation for this research is to advance the understanding on how drilled shafts react under loading in stiff clays and shales. The objectives of the study are to measure the strengths within the subsurface material at the test site, estimate the unit side shear and unit end bearing of the shale-shaft interaction by running two axial load tests, and compare the results to the current design methods that are used to predict the axial capacity of drilled shafts. A comprehensive field investigation, performed by Fugro Consultants, provided strength profiles of the subsurface material at the test site. Through the cooperation of the Texas Department of Transportation (TxDOT), the Association of Drilled Shaft Contractors, and McKinney Drilling Company, two drilled shafts were installed at a highway construction site in Austin, Texas. The load tests were performed by Loadtest, Inc.; using the patented Osterberg-Cell™ loading technique to axially displace the shafts. Ensoft, Inc. installed strain gauges at multiple levels within the shafts, making it possible to analyze the shaft mobilization during loading. Ultimate end bearing values of about 100- and 120-ksf were measured for Test Shafts #1 and #2, respectively. The current methods for estimating unit end bearing, developed by TxDOT and the Federal Highway Administration, provide fairly accurate predictions when compared to the measured information. The ultimate side resistance obtained near the O-Cell™ in each test was about 20-ksf, however, the measured ultimate side resistance steadily decreased nearing the tip of the shaft. For the zones where the side resistance was believed to be fully mobilized, the TxDOT design method accurately predicts the side resistance. A limited amount of information is currently available for load tests performed in soils with TCP values harder than 2-in per 100 blows. Additional load test information should allow for a stronger correlation between TCP tests and unit resistances for very hard clay-shales, as well as, allowing for further evaluation of the shale-shaft interaction near the shaft tip. The results presented herein demonstrate the effectiveness of the current design methods for drilled shafts and the non-uniformity of side resistance within one- to two-diameters of the shaft tip. / text

The VCOST budgeting tool uses a drive cycle simulator to improve fuel economy predictions for vehicle fleets. This drive cycle simulator needs to predict the efficiency of various components of the vehicle's powertrain including any differentials. Existing differential efficiency models either lack accuracy over the operating conditions considered or require too great an investment. A fundamental model for differential efficiency is a cost-effective solution for predicting the odd behaviors unique to a differential. The differential efficiency model itself combines the torque balance equation and the Navier-Stokes equations with models for gear pair, bearing, and seal efficiencies under a set of appropriate assumptions. Comparison of the model with existing data has shown that observable trends in differential efficiency are reproducible in some cases to within 10% of the accepted efficiency value over a range of torques and speeds that represents the operating conditions of the differential. Though the model is generally an improvement over existing curve fits, the potential exists for further improvement to the accuracy of the model. When the model performs correctly, it represents an immense savings over collecting data with comparable accuracy. / text