Transportation Intelligence

Volume 7 Number 4

August 2009
Safety
Administration
Traffic Control
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Pavement Design
Mechanistic Modeling of Unbound Granular Materials
Several tests are used for characterizing unbound granular materials for pavement applications. The California Bearing Ratio (CBR), resilient modulus (MR), Dynamic Cone Penetrometer (DCP) tests are three of the most common tests used for this purpose. The objective of this research is twofold. The first is to develop numerical models for these three tests. The second is to investigate relationship between basic material properties, boundary conditions, and test results, ultimately, to develop a physics-based correlation between these tests. A 3-D discrete element method (DEM) based model is adapted to simulate these tests. Good agreement is observed between the results of the simulations and sample numerical and experimental studies on granular materials. The DEM code is used to determine effects of aggregate shape, coefficient of friction, gradation, stiffness and other details on test results. The model is also used to investigate statistics of inter-particle interaction between the granular particles. (Minnesota Department of Transportation Research Report 2009-21, June 2009, 109 p.)

Administration
Cost Analysis of Alternative Culvert Installation Practices in Minnesota
Various factors associated with conventional culvert design, including shallow water, perched inlets and high flow velocities, can cause difficulties for migrating fish and affect their genetic diversity and long-term survival. Conventional culvert design has traditionally been based on hydraulic conveyance, safety and cost. Recently, some alternative culvert designs have been developed to facilitate salmon migration on the west coat of the United States. These alternative designs focus on matching the natural dimensions and characteristics of the stream channel through the culvert. The intended purpose of these newer designs is to provide unimpeded passage of aquatic life, reduce maintenance costs and improve erosion control. Currently, some of these new designs are being implemented in Minnesota mostly when fish passage is a consideration. There are concerns about the additional costs associated with these alternative designs as well as whether they are really needed at some road crossings. The objectives of this research were to summarize state-wide fish passage concerns related to culvert road crossings on public waters and to perform a cost comparison between the conventional and the alternative culvert designs. (Minnesota Department of Transportation Report MN/RC 2009-20, June 2009, 85 p.)
Urban
Design Flexibility Considerations for Built Urban Environments
In large cities, limited right-of-way, human and natural environmental issues, pedestrian and bicyclist accommodation, and aesthetic concerns often require a more contextual design to be used than in nonbuilt environments. It is therefore often required to develop unique solutions that may not conform to existing guidelines and require the use of design exceptions or variances. The objective of this report is, therefore, to (1) understand why such departures from the guidelines may be needed or desired, (2) identify processes that successfully manage such design procedures, and (3) determine means that could assist designers to streamline this process and provide a timely procedure for addressing design exceptions or variances. These three objectives were addressed though a survey of design and variance procedures of both local transportation agencies for large cities, as well as state departments of transportation (DOTs). (TRB National Cooperative Highway Research Program (NCHRP) Research Results Digest 337, June 2009, 29 p.+apps.)

Safety

International Scan Summary Report on Pedestrian and Bicyclist Safety and Mobility
In May 2009, a team of 12 transportation professionals with expertise in bicycling and walking from the United States (U.S.) visited five countries in Europe to identify and assess effective approaches to improve pedestrian and bicyclist safety and mobility. The countries were chosen because of their innovative approaches to nonmotorized transportation, as well as the potential transferability of their policies and practices. (US Federal Highway Administration International Technology Scanning Program Report, 24 June 2009, 11 p.)

Safety Evaluation of Advance Street Name Signs
The goal of this research was to evaluate and estimate the safety effectiveness of advance street name signs at signalized intersections in the Evaluation of Low-Cost Safety Improvements Pooled Fund Study (ELCSI-PFS), Phase II. This strategy is intended to reduce the frequency of older driver crashes and crashes related to way-finding (i.e., rear-end and sideswipe crashes) at signalized intersections. (US Federal Highway Administration Report FHWA-HRT-09-029, June 2009, 66 p.)

The influence of weather conditions on road safety - An assessment of the effect of precipitation and temperature
The influence of changes in extreme weather conditions is often identified as a cause of fluctuations in road safety and the resulting numbers of crashes and casualties. This report focuses on an analysis of the aggregate, accumulated effect of weather conditions (precipitation and temperature) on the number of road crashes and injuries in the Netherlands. (SWOV Research Report R-2009-9, 2009, 49 p.)

Subjective and Objective Safety - The Effect of Road Safety Measures on Subjective Safety among Vulnerable Road Users
The objective of the project has been to summarize the effect of 54 road safety measures on subjective safety among vulnerable raod users. The assessment is based on literature and theoretical considerations. The effect has only been directly studied for 14 measures and indirectly studied for another 14 measures. 39 measures are assessed to have a positive effect on subjective safety. Among 125 submeasures it is assessed that 78 have a positive effect on both objective and subjective safety and 25 have an opposite effect on objective and subjective safety, i.e. having positive effect on one parameter and negative effect on the other. 20 measures have an unknown or unclear effect on objective or subjective safety. Further investigation is relevant for at least 50 of the submeasures. 13 measures most relevant for further studies are selected. (Norwegian Institute of Transport Economics report 1009/2009, March 2009, 161 p.)

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Concrete

Ten-year field evaluation of corrosion-inhibiting systems in concrete bridges barrier walls
The performance of eight commercial corrosion-inhibiting systems was assessed in the field over ten years on reinforced concrete barrier walls of a highway bridge that was subjected to severe environmental conditions. These systems were composed of one or more of the following components: anticorrosion concrete admixtures, reinforcement coatings, and concrete surface coatings/sealers. The field evaluation consisted of annual surveys of corrosion potential and corrosion rate, as well as visual inspections and testing of concrete cores. After ten years, the main reinforcement of the barrier walls, at a depth of 75 mm [3 in.], was found in relatively good condition due to an initially good quality concrete. Special bars embedded at a depth of 13 mm [1/2 in.] in the barrier walls showed signs of advanced corrosion for all systems, however, no visible signs of corrosion were found on 25 mm [1 in.] deep bars. Non-destructive corrosion evaluation over the 25 mm [1 in.] deep ladder rebars indicated that the system containing the inorganic anticorrosion admixture provided consistently lower risks of corrosion, followed by systems containing organic anticorrosion admixtures, in comparison to the control system and other systems. The low concrete permeability and different stability of the protective layer forming on the bars may explain the observed differences in the effectiveness of these systems. (National Research Council of Canada report NRCC-50550, 1 May 2009, 10 p.)

Effectiveness of Cathodic Protection
The report provides a summary of Oregon’s experience with cathodic protection of coastal reinforced concrete bridges. Thermal-sprayed anodes, foil anodes with a conductive adhesive, and carbon painted anodes are effective in distributing current to the steel reinforcement in concrete bridges. (Oregon Department of Transportation Report SPR 345, June 30, 2009, 27 p.)

Investigation into Freezing-Thawing Durability of Low-Permeability Concrete with and without Air Entraining Agent
The aim of the present study is to investigate the effect of low-permeability concrete, made with reduced water-to-binder ratios (w/b) and/or supplementary cementitious materials (SCMs), on the need for air entrainment to achieve freezing-thawing (F-T) durability. In the present study, concrete mixes were made with different types of cement (Types I and IP), with or without fly ash replacement (15%), with different water-to-binder ratios (w/b =0.25, 0.35, 0.45 and 0.55), and with or without air entraining agent (AEA). All concrete mixtures were controlled to have a similar slump by using different dosages of superplasticizer. The rapid chloride permeability and F-T durability of the concrete samples were determined according to ASTM C1202 and ASTM C666A, respectively. The air void structure of the concrete was studied using the Air Void Analyzer, RapidAir, and porosity tests (ASTM C642). In addition, the general concrete properties, such as slump, air content, unit weight, and 28-day compressive strength, were evaluated. (Iowa State University - National Concrete Pavement Technology report, June 2009, 50 p.)

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Administration

Integrating the Priorities of Transportation Agencies and Utility Companies
This report documents current practices, opportunities for improvement, and anticipated barriers for integrating utility and transportation agency priorities in highway renewal projects. Thirteen best practices that span the whole project life cycle are also documented in a tool box format. Finally, the report provides a plan for future research in this field. (US Transportation Research Board Strategic Highway Research Program (SHRP 2) Report S2-R15-RW, 2009, 100 p.)

Maintenance Management 2009: Presentations from the 12th AASHTO-TRB Maintenance Management Conference
This publication contains papers presented at the 12th AASHTO–TRB Maintenance Management Conference held in Annapolis, Maryland, July 19–23, 2009. It includes papers on asset management, bridge monitoring and planning, environment, maintenance issues in design and construction, management systems, outsourcing and safety, pavement performance and preservation programs, performance-based contracting, quality assurance, roadside, winter services, and workforce development. (TRB’s Transportation Research Circular E-C135, July 2009, 320 p.)

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Traffic Control

Evaluation of Retroreflective Material on Stop Sign Posts in Virginia
The purpose of this study was to evaluate the effectiveness of retroreflective material on stop sign posts in Virginia with respect to visibility and driver compliance at the stop sign. The investigation included a review of the feasibility, costs, and benefits of this application. In addition, a review of practices by other localities and DOTs was performed and field studies were conducted to examine visibility and driver compliance. (Virginia Transportation Research Council Report VTRC-09-R23, June 2009, 37 p.)

Synthesis of Benefits and Costs of Alternative Lane Marking Strategies
The Virginia Department of Transportation (VDOT) currently uses snowplowable raised pavement markers (SRPMs) to supplement longitudinal pavement markings on some facilities. SRPMs are much more visible than traditional longitudinal markings under wet, nighttime conditions. SRPMs have been reported to dislodge from pavement, however, which has raised the question as to whether alternative marking materials might be able to replace SRPMs. The purpose of this study was to investigate the visibility performance of longitudinal pavement marking materials currently on the market. The study primarily synthesized existing research on the characteristics of different marking materials and then applied information derived from the synthesis to Virginia-specific data to estimate the impacts of using different materials. National practices for installing, inspecting, and maintaining SRPMs were also reviewed. (Virginia Transportation Research Council report VTRC 09-R24, May 2009, 57 p.)

Use of Graphics and Symbols on Dynamic Message Signs: Technical Report
This project has taken a step toward defining how graphic and symbol displays can improve or assist communication with drivers. Through three human factors evaluations of alternative designs, researchers identified specific design elements that should or should not be used in graphic displays. Additionally, some of the key benefits identified for the use of graphic displays as compared to equivalent text messages are: - A graphic display appears to improve the ability of drivers to identify available lanes in a problem area. - The delivery of incident descriptor information (e.g. accidents or work zone) through the use of graphic symbols improves comprehension levels of non-native-language drivers (e.g., a driver whose primary language is Spanish. - The viewing time required for comprehension by a non-native speaker may be shortened as a result of the use of graphics and symbols. - The use of graphics makes it possible to effectively illustrate unusual operational scenarios, such as high-occupancy vehicle lanes or adjacent toll lanes, through graphic representation of roadway geometry, logos, shields, etc. (Texas Department of Transportation Report FHWA/TX-08/0-5256-1, May 2009, 192 p.)

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