Texas Transportation Researcher

Quarterly newsletter of the Texas Transportation Institute discussing the research, professional, and service activities of the organization as well as general research and innovations related to transportation in Texas

Texas Transportation Researcher

Quarterly newsletter of the Texas Transportation Institute discussing the research, professional, and service activities of the organization as well as general research and innovations related to transportation in Texas

Texas Transportation Researcher

Quarterly publication of the Texas A&M Transportation Institute discussing their research as well as professional and service activities. It includes articles about research and innovations in various areas related to transportation in Texas

Indirect methods to account for exposure in highway safety studies

DTFH61-93-R-00123One of the more complex issues in highway safety evaluation is how to incorporate some measure of exposure, some numerical measure of the opportunity for an accident to occur in the analysis. On a roadway section, for example, exposure might be vehicle-miles traveled (VMT). At fixed points, such as intersections, exposure might be some function of the annual average daily traffic (AADT) of the intersecting roads. However, the appropriate measure of exposure may not be at all clear, such as in driver- or vehicle-based analyses. In assessing the involvement of older drivers in left-turn accidents, for example, how does one measure the exposure of drivers by age at a specific site? Because of the difficulty of obtaining numerical exposure estimates, indirect methods have evolved for treating the exposure issue in a surrogate manner. This report is intended to be an instructional text on these methods for use by the highway safety research community. The indirect methodologies presented here include before/after evaluation designs, case-control studies, and the induced-exposure methodologies. The numerical computations for each methodology are presented in simple, step-by-step formulas, followed by a numerical example. A discussion of both the advantages and disadvantages and appropriate and inappropriate applications are also presented. It is hoped that this report will serve as a comprehensive guide for the highway safety researcher, both in designing and in evaluating highway safety studies

Texas Transportation Researcher

Quarterly publication of the Texas A&M Transportation Institute discussing their research as well as professional and service activities. It includes articles about research and innovations in various areas related to transportation in Texas

Texas Transportation Researcher

Quarterly publication of the Texas A&M Transportation Institute discussing their research as well as professional and service activities. It includes articles about research and innovations in various areas related to transportation in Texas

Safety Implications of Various Truck Configurations, Volume III: Summary Report

DTFH61-85-C-00091The purpose of this study is to examine changes to size and weight limits in order to determine their effects on the designs and configurations of heavy vehicles, the performance capabilities of the resulting vehicles, and the ensuing safety implications thereof. The summary report provides results and findings from an analytical investigation of the influences of size and weight limits on trucks. In an analytical sense, pavement loading rules and bridge formulas are the inputs to the analyses and vehicle performances are the outputs. Ultimately, the work shows the manner in which size and weight rules influence the safety-related performance of vehicles designed to increase productivity. By treating a number of projected size and weight scenarios, the study has developed a basis for generalizing to sets of principles that can be used in evaluating the possible safety consequences of changes in size and weight regulations

Texas Transportation Researcher

Quarterly publication of the Texas A&M Transportation Institute discussing their research as well as professional and service activities. It includes articles about research and innovations in various areas related to transportation in Texas

Safer Bridge Railings, Volume I: Summary Report

DOT-FH-11-9181This study consisted of strength analyses of five in-service bridge railing systems, thirty full-scale vehicle crash tests on those railing systems and on a load measuring wall, the development of recommended design guidelines and development of recommended performance standards. The spectrum of vehicles addressed ranged from an 1,800 lb Honda sedan to a 32,000 lb intercity bus. Some of the in-service railings were found to have poor performance in full-scale crash tests. This was primarily due to geometry of the railing; however, deficiencies in strength were also discovered. This report consists of four volumes. (Volume 1: Summary Report FHWA/RD-82/072; Volume 2: Appendices A, B, D and E FHWA/RD-82/073; Volume 3: Appendix C, Part I FHWA/RD-82/074.1; and Volume 4: Appendix C, Part II FHWA/RD-82/074.2.

Use of Tamper Bar Paver to Place Thick-Lift Asphalt Concrete Pavement [Summary]

0-7064Asphalt concrete placement specifications have maximum allowable lift thicknesses to ensure adequate mixture compaction. When the design thickness exceeds this limit, placement must be phased in multiple lifts, creating other problems: - Increased construction time, traffic exposure, and traffic disruption; - Potentially worse performance from poor stiffness/bonding at the lift interface. In 2018, an Atlanta District contractor experimented with a tamper bar paver for single-lift placement of Superpave Type C at four (4) to six (6) inches thick. Both the top and bottom of the lift had acceptable air void contents. Further study of tamper bar pavers for thick-lift construction is warranted. The research team will: (1) Review the literature for performance of tamper bar pavers in thick-lift placement and recommended maximum lift-thicknesses. (2) Develop a field-based testing plan that considers different construction scenarios, paver types, number of lifts, total thickness, tamper bar settings, and roller patterns. (3) Construct test sections and evaluate in-place air voids with traditional methods and innovative methods like full-coverage Ground Penetrating Radar (GPR) based density testing and Computed Tomography (CT) X-ray scanning. Also evaluate pavement profile roughness, and stiffness and cracking performance of cores. (4) Statistically analyze the data. (5) Develop guidelines for the use of tamper bar pavers, highlighting best practices and limitations