Jeffrey David Miles

Evaluation of Operational Impacts of Installation of Centerline and Edge Line Rumble Strips

Research findings have shown that centerline rumble strips (CRSs) and shoulder rumble strips (SRSs) have significant safety benefits. SRSs have proved successful in reducing run-off-the-road crashes, and more recent research has shown that CRSs can potentially reduce head-on collisions. However, concerns about the operational effects of CRSs and SRSs remain. Specifically, how do the installations affect vehicle lateral position, passing operations, and shoulder usage? This paper documents the findings of research conducted for the Texas Department of Transportation on CRSs and edge line rumble strips (ERSs), a variation on SRSs that are placed directly on the marked edge line. Before-and-after analyses were conducted on Texas highways where CRSs or ERSs, or both, were installed. CRSs were evaluated with respect to passing operations and vehicle lateral position within the travel lanes; ERSs were evaluated for shoulder usage and vehicle lateral position during shoulder encroachments. The results of the stu...

Evaluation of Alternative Procedures for Setting Curve Advisory Speed

This paper examines procedures for setting curve advisory speeds, identifies issues associated with these procedures, and describes a proposed procedure that overcomes many of these issues. The proposed procedure consists of three elements: a criterion for setting the curve advisory speed, a method for determining this speed, and an engineering study method that confirms the need for an advisory speed plaque. One conclusion is that challenges associated with the use of the ball-bank indicator hinder achieving curve advisory speeds that are uniform in curves and consistent with driver expectation. The proposed procedure is shown to overcome these challenges.

Analysis of In-Service Traffic Sign Retroreflectivity and Deterioration Rates in Texas

Roadway traffic signs are a fundamental medium for conveying critical information to the road user. In 2009, the Manual on Uniform Traffic Control Devices (MUTCD) set minimum retroreflectivity requirements for such signs. Developing sign management strategies on the basis of service life is one approach to achieving compliance with minimum MUTCD sign retroreflectivity requirements. Generating deterioration rates and prediction models from a sample of in-service sign measurements is one method for establishing expected service life. In 2009, researchers collected a sample of 859 ASTM D4956 Type III retroreflectivity signs in seven regions of Texas. The objective of this study was to assess the compliance of Type III signs throughout Texas and to generate useful data that would improve sign maintenance practices. The overall sign sample compliance rate was 99%. The observed likelihood of failure was 2% for signs that were between 10 and 12 years old and 8% for signs that were 12 to 15 years old. The linear prediction models revealed differences in deterioration rates between the regions. The differences ranged from −2 to −8 candelas (cd)/lx/m2 per year for white sheeting and −1 to −12 cd/lx/m2 per year for yellow sheeting. Models exhibited poor correlations between predicted and measured data, and the R-squared values ranged from .10 to .30. Despite the weak relationships, the models revealed insightful trends and provided a broad perspective on the Texas Department of Transportations current sign practices. Deterioration rates and prediction models can be valuable components in a comprehensive sign maintenance program, but by themselves they do not ensure compliance with sign retroreflectivity requirements.

Nighttime Visibility of Prototype Work Zone Markings Under Dry, Wet-Recovery, and Rain Conditions

This paper presents the findings of a dynamic pavement marking visibility study conducted as part of the FHWA Highways for LIFE Technology Partnerships Program Temporary Wet-Weather Pavement Markings for Work Zones project. Three prototype optics-on-paint marking systems employing high refractive index dual-optics drop-on elements were evaluated at night under dry, wet-recovery (immediately after rainfall), and rain conditions. These three prototypes were chosen based on their durability from an initial pool of 22 experimental systems evaluated in a test deck. This dual-optic system was designed to provide good visibility in both dry and wet weather conditions. Two commercially available marking systems were also evaluated as industry benchmarks (one glass beads-on-paint system, one wet-reflective removable tape). Thirty participants driving through simulated work zones on a closed course viewed all of the marking types at night under all three weather conditions. Each drivers task was to identify the direction of work zone lane shift tapers delineated by the markings. In wet recovery, all three prototype marking systems and the wet-reflective tape sustained 60% to 80% of their dry average detection distances, and in rain, they sustained 50% to 70% of their dry average detection distances. In contrast, the average wet-recovery and rain detection distances for the conventional glass beads-on-paint benchmark system dropped to 28% and 17% of the dry detection distance, respectively. In addition, participants failed to detect the conventional glass beads-on-paint benchmark system in nearly half of the observations in the rain condition.