CTR Library's Research Digest, September 2010

Research Digest FORWARD ALL REQUESTS TO: The University of Texas at Austin Center for Transportation Research LIBRARY 1616 Guadalupe St. | Suite 4.202 | Austin, Texas 78701 Phones: (512) 232-3126 and (512) 232-3138 Email: ctrlib@austin.utexas.edu In this Issue:

State DOT Reports

Table of Contents Item 1.

Asset Management Inventory and Data Collection (FHWA-NC-2008-15)............................... 1

Item 2.

Transition from Manual to Automatic Rutting Measurement (NM08SAF-023)........................2

Item 3.

Bridge Deck Concrete Volume Change (VTRC 10-CR5)..........................................................2

Item 4.

Field Performance of High Friction Surfaces (VTRC 10-CR6)................................................. 3

Item 5.

Methods for Assessing the Polishing Characteristics of Coarse Aggregates for Use in Pavement Surface Layers (VTRC 10-CR7)............................................................................... 4

Item 6.

Multivariate Volumetric Specifications and Dynamic Modulus as a Quality Measure for Asphalt Concrete Materials (VTRC 10-CR8).......................................................................5

Item 7.

Effect of Wet Curing Duration on Durability Parameters of Hydraulic Cement Concretes (VTRC 10-R11)........................................................................................................ 6

Item 8.

Evaluation of Driver Reactions for Effective Use of Dynamic Message Signs in Richmond, Virginia (VTRC 10-R16)......................................................................................... 7

Item 9.

Laboratory Investigation of Nanomaterials to Improve the Permeability and Strength of Concrete (VTRC 10-R18)...................................................................................................... 8

Item 10.

Access Management Performance Measures for Virginia (VTRC 10-R2).................................9

Item 11.

Work Zone Variable Speed Limit Systems (VTRC 10-R20)....................................................10

Item 12.

Causal Factors for Intersection Crashes in Northern Virginia (VTRC 10-R22)........................10

Item 13.

Investigation of the Use of Tear-Off Shingles in Asphalt Concrete (VTRC 10-R23)...............11

Item 14.

Short-Term Evaluation of a Bridge Cable Using Acoustic Emission Sensors (VTRC 10-R24)......................................................................................................................................11

Item 15.

Development of Safety Performance Functions for Two-Lane Roads Maintained by the Virginia department of Transportation (VTRC 10-R25).....................................................12

Item 16.

An Examination of Practices for Retrofitting Existing Roads with Sidewalks in the United States (VTRC 10-R4).....................................................................................................12

Item 17.

Investigation of the Rolling Wheel Deflectometer As a Network-Level Pavement Structural Evaluation Tool (VTRC 10-R5)................................................................................13

Item 18.

Investigation of Fiber-Reinforced Self-Consolidating Concrete (VTRC 10-R8)......................14

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Research and Technology Implementation Office

September 2010

Research Digest Item 1 Asset Management Inventory and Data Collection NORTH CAROLINA DEPARTMENT OF TRANSPORTATION (NCDOT) FHWA-NC-2008-15 • 2009 An efficient and accurate inventory of a state highway agency's assets, along with the means to assess the condition of those assets and model their performance, is critical to enabling an agency to make informed investment decisions in a Transportation Asset Management (TAM) environment. Today, new technologies provide fast and improved ways to gather, process, and analyze data. The key is to identify and gather the most useful, reliable, cost-effect information and use it to make informed decisions for asset management.

Four key infrastructure areas have been identified as primary asset components; pavements, bridges, geotechnical features, and roadside appurtenances. Each area contains multiple categories and data elements important for sound decision making. Although some similarities exist in these four primary categories, the nature of data collection may differ, depending on the asset type. The sheer number of data elements and the length of asset networks for pavements and roadside appurtenances render the automated highway speed data collection method a necessity rather than a luxury. However, the discrete nature of bridges and geotechnical features make the automated mobile data collection method on a network level unfeasible with today's technology.

Important issues in the collection process include precision, subjectivity and variability of the process itself, as well as speed, safety of the survey crew, proximity of the public, cost, etc. Although previous research has attempted to address these issues and determine the most appropriate method(s), the question remains as to which roadway data collection system is best for state highway agencies given real world constraints. This research set up a "sealed envelope" experiment wherein the identification, location, description, and quality of the asset data elements are known only to NCSU researchers. Vendors are informed of only the data necessary to perform their evaluation. To support this effort at 95-mile test course near Raleigh, North Carolina was identified, which contained a sampling of pavement, roadside, geotechnical and bridge elements. This document reports on the findings from the study.

Full-text PDF of this report is available for free download from: http://www.ncdot.org/doh/preconstruct/tpb/research/download/2008-15finalreport.pdf

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Research and Technology Implementation Office

September 2010

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Research Digest Item 2 Transition from Manual to Automatic Rutting Measurement : Effect on Pavement Serviceability Index Values NEW MEXICO STATE UNIVERSITY. DEPARTMENT OF CIVIL ENGINEERING NM08SAF-023 • 2010 The research reported herein aimed to develop a procedure or protocol to transition from using rutting ratings from manual surveys to using automated rut depth measurements for calculating the New Mexico Department of Transportation's (NMDOT) Pavement Serviceability Index (PSI). One recommended approach and an alternative procedure are presented. One of the main motivations of NMDOT to implement this change was to increase the safety of distress survey crews and the travelling public by eliminating the need for performing manual rut depth measurements in the roadway during the annual manual surveys. The MNDOT was also interested in avoiding duplication of efforts resulting from collecting rut depth data by two different methods.

"A report on research sponsored by New Mexico Department of Transportation Research Bureau in cooperation with the U.S. Department of Transportation Federal Highway Administration" Full-text PDF of this report is available for free download from: http://bit.ly/nmshtd_state_nm_us_Report_nm08saf-023_52MB-large-PDF http://nmshtd.state.nm.us/upload/images/Research/NM08SAF-02_Presentation_Appendix_G_06-28-10.pdf

Item 3 Bridge Deck Concrete Volume Change VIRGINIA TRANSPORTATION RESEARCH COUNCIL (VTRC) VTRC 10-CR5 • 2010 Concrete structures such as bridge decks, with large surface area relative to volume, shrink and crack, thus reducing service life performance and increasing operation costs.

The project evaluated the early, first 24 hours, and long-term, 180 days, shrinkage of Virginia Department of Transportation overlay and A4 general bridge deck concrete mixtures. A modified ASTM C157 prism was developed to measure the early-age shrinkage, as was a unique hygral cylinder test. Long-term shrinkage was measured using the ASTM C157 prism test. In addition, scaled bridge deck overlay specimens were cast to assess cracking potential. Overlay mixtures tested were latex modified mixtures using portland cement, Type K cement, an expansive mixture and portland cement, fly ash and microsilica blend. Deck concrete mixtures evaluated were fly ash, slag, Type K cement and an expansive mixture.

Recommendations for controlling shrinkage at 3, 7, and 28 days were developed for all overlay and A4 concrete mixtures.

Full-text PDF of this report is available for free download from: http://www.virginiadot.org/vtrc/main/online_reports/pdf/10-CR5.pdf

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Research and Technology Implementation Office

September 2010

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Research Digest Item 4 Field Performance of High Friction Surfaces : Final Contract Report VIRGINIA TRANSPORTATION RESEARCH COUNCIL (VTRC) VTRC 10-CR6 • 2010 This report describes an evaluation of high friction surface (HFS) systems. The goal of this evaluation was to develop guidance for agencies when considering whether an HFS was an appropriate solution when addressing specific instances of low skid resistance and/or especially high friction demand. HFS systems are specially designed thin surface treatments that provide significant additional skid resistance of pavements and bridge decks without significantly affecting other qualities of the surface such as noise, ride quality, or durability. This report documents the location and climatic conditions where some of these systems are placed, recounts the experiences reported by the agencies that were responsible for their placement, and summarizes key HFS servicelevel indicators (friction and texture).

The agency experiences include a sample benefit-cost analysis from an installation in Wisconsin that justified an HFS application through crash reductions that resulted following the measured increase in skid resistance.

Analysis of the service level indicators included development of the coefficients necessary to obtain the International Friction Index (IFI) values for each of the tested systems. Review of the IFI values suggested that more experiments with different types of wearing surfaces, to include HFS systems as well as more conventional surface treatments, are necessary in order to demonstrate the validity of the speed gradient and friction coefficients recommended by the ASTM standard for the IFI. Supplementary Notes: This study is based upon work supported by the Federal Highway Administration and the U.S. Surface Properties Consortium under pool fund award TPF-5(141). Virginia serves as the leading state; the Virginia Transportation Research Council managed the project.

Full-text PDF of this report is available for free download from: http://www.virginiadot.org/vtrc/main/online_reports/pdf/10-CR6.pdf

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Research and Technology Implementation Office

September 2010

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Research Digest Item 5 Methods for Assessing the Polishing Characteristics of Coarse Aggregates for Use in Pavement Surface Layers VIRGINIA TRANSPORTATION RESEARCH COUNCIL (VTRC) VTRC 10-CR7 • 2010 The predominant aggregate resources located in the western parts of Virginia are carbonate rocks. The mineral components of these rocks tend to be relatively soft and subject to abrasive wear under traffic that leads to a fairly rapid smoothing of the aggregate surface and the surface of pavements containing them. This smoothing or polishing leads to a loss of surface friction and thus skid resistance of the pavement, creating potential safety issues. As a consequence, surface courses of pavements are constructed with nonpolishing aggregates, which in the western districts can mean lengthy transport of materials. With rising economic and environmental costs associated with transportation, increasing the use of locally available materials through improved methods to discern subtle differences in polishing tendencies or blending of polishing with nonpolishing aggregates could translate into significant cost savings.

In this study, a suite of carbonate aggregates suspected to show a range of polishing characteristics based on previous studies was selected for evaluation along with several sources currently used as nonpolishing aggregates.

The aggregates were examined petrographically, and the carbonate sources were tested for insoluble residue and subjected to a dilute acid etch to form the basis for a tentative classification of polishing susceptibility. The aggregates were tested in the Micro-Deval apparatus using both the standard procedure for coarse aggregates and a cyclical A/P procedure with silica sand devised for this study to examine how the various aggregate types responded when subjected to various degrees of wearing under similar conditions.

Full-text PDF of this report is available for free download from: http://www.virginiadot.org/vtrc/main/online_reports/pdf/10-CR7.pdf

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Research and Technology Implementation Office

September 2010

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Research Digest Item 6 Multivariate Volumetric Specifications and Dynamic Modulus as a Quality Measure for Asphalt Concrete Materials : Contract Report VIRGINIA TRANSPORTATION RESEARCH COUNCIL (VTRC) VTRC 10-CR8 • 2010 The Virginia Department of Transportation (VDOT) has worked toward end-result specifications (ERSs) in asphalt concrete since the mid-1960s. As stated by Hughes et al. (2007), true ERSs can lead to a reduction in VDOT’s overall inspection force resulting in considerable savings and allow for the reallocation of inspection resources to key construction and placement processes that cannot be measured upon delivery (e.g., joint tacking and construction platform preparation). The latest efforts toward this end were conducted by Hughes et al.

(2007) who suggested expanding the quality measures for asphalt concrete acceptance to include the asphalt concrete volumetric properties of voids in total mix (VTM) and voids in mineral aggregates (VMA), along with the already used asphalt content (AC) and gradation. This report builds on that and further investigates, through the use of the asphalt concrete dynamic modulus, how performance-related ERSs can be introduced into a quality assurance (QA) plan.

Specifically, the report:(1) documents the current variability of VTM, VMA, and AC; (2) explores different QA specification plans; and (3) develops and applies a method to predict asphalt concrete rutting performance from asphalt concrete dynamic modulus test results using the mechanistic-empirical pavement design guide (MEPDG).

Full-text PDF of this report is available for free download from: http://www.virginiadot.org/vtrc/main/online_reports/pdf/10-CR8.pdf

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Research and Technology Implementation Office

September 2010

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Research Digest Item 7 Effect of Wet Curing Duration on Durability Parameters of Hydraulic Cement Concretes VIRGINIA TRANSPORTATION RESEARCH COUNCIL (VTRC) VTRC 10-R11 • 2010 Hydraulic cement concrete slabs were cast and stored outdoors in Charlottesville, Virginia, to study the impact of wet curing duration on durability parameters. Concrete mixtures were produced using portland cement, portland cement with slag cement, and portland cement with Class F fly ash concretes with water's cementitious materials ratios (w/cm) of 0.45 and 0.35. These concretes were subjected to immediate liquid membrane-forming curing or 1, 3, 7, or 14 days wet curing. Two slabs were cast for each of the wet curing durations. Following the curing period, one slab was allowed to dry naturally, and liquid membrane-forming curing compound was applied to the other. Three additional concretes containing saturated lightweight fine aggregate were produced to study the potential impact of internal curing on the durability parameters. These concretes contained portland cement with fly ash, silica fume, and both, at 0.35 w/cm. Three slabs were cast from each mixture and subjected to liquid membrane-forming curing, 1 or 3 days wet curing. The slabs were instrumented with humidity probes at two depths below the surface. Specimens were removed from two depths and tested for tensile strength, electrical conductivity, and sorptivity at 3 and 12 months of age.

The success rate of the humidity measurements within the slabs was low because of water condensation.

However, water condensation qualitatively indicates that the slabs did not dry out to an extent that would adversely impact concrete property development. Neither the strength, electrical conductivity, nor sorptivity results were impacted appreciably by the duration of moist curing. At most, 1 to 3 days wet curing was sufficient.

Reducing w/cm had a positive impact on reducing permeability parameters, and previous work by others has shown the duration of curing needed to achieve discontinuity in the capillary pore system decreases with decreasing w/cm. No added benefit was observed by application of liquid membrane-forming curing following the wet curing. The prevailing weather conditions in the months during and following placement were humid, which would obviate any benefit from post wet-curing applications of liquid membrane-forming curing compound to slow drying. Prevailing weather conditions and the w/cm of the concrete mixture are important factors in determining adequate curing procedures and duration and should be considered by the project management team at the time of construction to establish appropriate procedures.

A direct cost savings could be realized by removing the requirement for wet curing and using LMFC only in situations where it is likely to benefit the curing process. Alternatively, there may be long-term benefits that could be realized by applying these cost savings to the application of penetrating sealers, particularly for concretes that will be subjected early in their life to aggressive anti-icing and deicing programs.

Full-text PDF of this report is available for free download from: http://www.virginiadot.org/vtrc/main/online_reports/pdf/10-r11.pdf

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Research and Technology Implementation Office

September 2010

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Research Digest Item 8 Evaluation of Driver Reactions for Effective Use of Dynamic Message Signs in Richmond, Virginia VIRGINIA TRANSPORTATION RESEARCH COUNCIL (VTRC) VTRC 10-R16 • 2010 Dynamic message signs (DMS) are used in conjunction with other media to communicate traffic conditions, general information, and recommended diversion strategies to motorists. Previous studies using loop detector data to estimate diversion rates attributable to advisory messages on DMS have found that diversion is minimal when vague messages are displayed or a distant alternate route is the only option. For motorists traveling on I-95 through Richmond in the Virginia Department of Transportation's Central Region, however, when DMS alert motorists of incidents, I-295 serves as a comparable alternate route, adding no significant travel time to through trips. This scenario provides the opportunity to evaluate the effectiveness of DMS in traffic diversion without the major concerns of added trip time and the quality of the route.

This study investigated the impacts of existing message strategies to determine messages that maximize diversion for specific circumstances and to develop new messages for future deployment. An analysis was done for various message types and split into two diversion scenarios: (1) an incident on the primary freeway, I-95, encourages diversion of I-95 traffic to an alternate route, I-295; and (2) an incident on an intersecting freeway, I295, encourages exiting I-295 traffic to remain on I-95 as an alternate route. The results showed trends where the use of particular words in messages is more effective than the use of others in achieving diversion when percentage of diverted traffic was used as the performance measure.

The effects on traffic flow by drivers' reactions to non-traffic messages were also investigated. Transportation agencies are frequently asked to post public service announcements on DMS when they are not being used for traffic-related purposes. It has been suggested that these messages are a distraction to drivers and result in queuing, creating mobility and safety hazards. An analysis that used speed as the performance measure showed minimal impacts on traffic flow from the display of non-traffic messages during weekday non-peak hours.

The study recommends that (1) travel time estimates for both the primary and alternate routes or the length or time of the delay be provided on DMS; (2) specific wording, as noted in the text, be used to induce diversion or simply to provide information; (3) messages be displayed in "title case" instead of "ALL CAPS" (i.e., all letters in a word are capitalized) for low frequency messages; and (4) left-justified or "staircase" messages be used.

Further, non-traffic messages should be one-phase messages and should be displayed only during non-peak periods to minimize the potential for queuing.

If the recommendations of this research are implemented, the enhanced effectiveness of diversion strategies will result in reductions of delay, fuel consumption, and emissions, as well as the potential for secondary accidents created by major incidents and other traffic flow disruptions. In 2007, the cost of delay for motorists in Richmond, Virginia, resulting from incidents was estimated at $119 million. A modest 1 percent reduction in this cost attributable to better diversion strategies that use DMS more effectively would result in an annual cost savings to VDOT of more than $1 million.

Full-text PDF of this report is available for free download from: http://www.virginiadot.org/vtrc/main/online_reports/pdf/10-r16.pdf

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Research and Technology Implementation Office

September 2010

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Research Digest Item 9 Laboratory Investigation of Nanomaterials to Improve the Permeability and Strength of Concrete VIRGINIA TRANSPORTATION RESEARCH COUNCIL (VTRC) VTRC 10-R18 • 2010 Concretes containing various supplementary cementitious materials (SCMs) such as silica fume, fly ash, and slag have improved properties. Nanomaterials (a nanometer, nm, is 10-9 m), new SCMs with possible applications in concrete, have the smallest particle size that is less than 100 nm. Nanomaterials are very reactive because of the particles' small size and large surface area and have great potential in improving concrete properties such as compressive strength and permeability. This study evaluated the use of a variety of nanomaterials in concrete compared with conventional concrete and concrete containing common SCMs. The potential benefits of using nanomaterials over other SCMs are their high reactivity; the need for smaller amounts, resulting in less cement replacement; and cost-effectiveness.

Concretes containing nanosilica and nanoclay were prepared in the laboratory and compared to concretes containing silica fume, fly ash, slag, or only portland cement. Specimens were tested for compressive strength and permeability. The microstructure of selected concretes with improved compressive strength and permeability were analyzed using an atomic force microscope and nanoindenter to determine the reason for the improvements.

The microstructure of the nanosilica concrete was denser and more uniform than that of the conventional concrete microstructure. In addition, the nanosilica had the largest improvement in both compressive strength and permeability among the nanomaterials tested.

The results of this study indicate that some of the nanomaterials tested have potential in concrete applications.

However, further evaluation is required before nanomaterials can be used in concrete. Specifically, they should be evaluated for improved dispersion to achieve uniformity, optimized amounts of ingredients, and costeffectiveness.

Full-text PDF of this report is available for free download from: http://www.virginiadot.org/vtrc/main/online_reports/pdf/10-r18.pdf

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Research and Technology Implementation Office

September 2010

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Research Digest Item 10 Access Management Performance Measures for Virginia : A Practical Approach for Public Accountability VIRGINIA TRANSPORTATION RESEARCH COUNCIL (VTRC) VTRC 10-R2 • 2010 In order to develop performance measures to communicate the effect of Virginia's access management program, five tasks were performed: (1) the appropriate literature was reviewed, (2) a catalog of potential performance measures was developed, (3) potential users of the performance measures were surveyed, (4) promising measures were tested, and (5) measures were recommended.

The literature review yielded a catalog of 42 potential performance measures. These measures are based on five goals and nine objectives related to the desired outcomes of the access management program. The five goals are reduce congestion, enhance safety, support economic development, reduce the need for new highways, and preserve the public investment in highways. Seven objectives are design elements: reduce conflict points, provide adequate distance between signals, provide adequate distance between unsignalized access points, add medians and two way left turn lanes, add dedicated turn lanes, restrict median openings, and use frontage roads and supporting streets. Two objectives are administrative elements: to enhance cooperation between agencies, and plan for future development.

Full-text PDF of this report is available for free download from: http://www.virginiadot.org/vtrc/main/online_reports/pdf/10-r2.pdf

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Research and Technology Implementation Office

September 2010

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Research Digest Item 11 Work Zone Variable Speed Limit Systems : Effectiveness and System Design Issues VIRGINIA TRANSPORTATION RESEARCH COUNCIL (VTRC) VTRC 10-R20 • 2010 Variable speed limit (VSL) systems have been used in a number of countries, particularly in Europe, as a method to improve flow and increase safety. VSLs use detectors to collect data on current traffic and/or weather conditions. Posted speed limits are then dynamically updated to reflect the conditions that motorists are actually experiencing. Presenting drivers with speed limits that are appropriate for current conditions may reduce speed variance, a concept sometimes called speed harmonization. If properly designed, VSL systems have been shown to reduce crash occurrence and can also reduce system travel time through increased uniformity in traffic speeds.

High-volume urban work zones tend to be prone to congestion and safety problems, and VSLs may be one way to ameliorate these issues. VSLs were recently installed at a high-volume, congested urban work zone located on I-495 (the Capital Beltway, hereinafter the Beltway) between the Springfield Interchange in Springfield, Virginia, and the Virginia-Maryland state line on the Woodrow Wilson Memorial Bridge. VSL signs were activated in late July 2008, but initial evaluations of the system showed inconclusive effects. Changing site conditions made a direct before-and-after evaluation of the system deployed in the field problematic, and some problems with the control algorithm were also noted.

Given the difficulties in evaluating the system deployed in the field, a calibrated simulation of the site was constructed to assess the effects of the VSL system on traffic operations and safety surrogate measures. The simulation platform also provided an opportunity to examine a number of system configurations to assess how changes in system design and driver behavior might affect a variety of measures. The results indicated that the VSL could create substantial improvements in traffic operations provided the demand did not exceed capacity by too large a margin. The location of the VSL signs played an important role in operational performance.

The study recommends that the Virginia Department of Transportation continue to pursue this technology but carefully scrutinize algorithm design and VSL sign placement. Further, a cost/benefit analysis indicated that VSLs may be most appropriate for long-term applications.

Full-text PDF of this report is available for free download from: http://www.virginiadot.org/vtrc/main/online_reports/pdf/10-r20.pdf

Item 12 Causal Factors for Intersection Crashes in Northern Virginia : Final Report VIRGINIA TRANSPORTATION RESEARCH COUNCIL (VTRC) VTRC 10-R22 • 2010 Intersection crashes cost the nation more than $40 billion annually, account for more than one-fifth of all highway crash fatalities nationally, and totaled almost 75,000 in the Virginia Department of Transportation’s (VDOT) Northern Virginia District for the period 2001 through 2006. Although VDOT maintains several databases containing more than 170 data elements with detailed crash, driver, and roadway attributes, it was not clear to users of these databases how these data elements could be used to identify causal factors for these intersection crashes for two reasons: (1) the quality of some of the data elements was imperfect, and (2) and random variation is inherent in crashes. This study developed an approach to address these two issues.

Full-text PDF of this report is available for free download from: http://www.virginiadot.org/vtrc/main/online_reports/pdf/10-r22.pdf

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Research and Technology Implementation Office

September 2010

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Research Digest Item 13 Investigation of the Use of Tear-Off Shingles in Asphalt Concrete VIRGINIA TRANSPORTATION RESEARCH COUNCIL (VTRC) VTRC 10-R23 • 2010 This investigation focused on the use of asphalt shingles that had been removed from roofs and recycled into asphalt concrete. Upon invitation by the Virginia Department of Transportation (VDOT), three asphalt contractors produced and placed sections of asphalt concrete containing shingles. The sections were sampled and tested by the Virginia Transportation Research Council. Two base mixes and two surface mixes were produced, and one of the surface mixes was produced by both hot mix and warm mix technology. The laboratory tests used to evaluate the mixes were tests to determine conventional gyratory volumetric properties, gradation, and asphalt content; rut tests; fatigue tests; and tests to determine recovered asphalt properties.

Satisfactory test results and good paving experiences with regard to the field installations indicated that mixes containing tear-off shingles can be constructed successfully. According to cost estimates, in 2009, VDOT could have saved approximately $600,000 by using 4 to 5 percent shingle waste in one-half of the hot mix produced.

VDOT plans to adopt the special provision used for this study with minor modifications as a general specification for paving in 2010.

Full-text PDF of this report is available for free download from: http://www.virginiadot.org/vtrc/main/online_reports/pdf/10-r23.pdf

Item 14 Short-Term Evaluation of a Bridge Cable Using Acoustic Emission Sensors VIRGINIA TRANSPORTATION RESEARCH COUNCIL (VTRC) VTRC 10-R24 • 2010 The Varina-Enon Bridge carries I-295 across the James River and crosses over the shipping channel that leads to the Richmond (Virginia) Marine Terminal. The bridge is a cable-stayed bridge that was opened to traffic in July 1990. It has 150 ft of vertical navigational clearance and 630 ft of horizontal navigational clearance. The overall bridge length is 4,686 ft. The bridge has six lanes (three each way) with full right and left shoulders.

This study used acoustic emission (AE) to assess the condition of strands by examining for active defects (such as corrosion, crack expansion and rubbing, wire breaks, and similar active defects) on a single stay-cable, from anchorage point to anchorage point, of the Varina-Enon Bridge. Testing was performed over short durations of time during periods that included low traffic volumes (acoustically quiet) and high traffic volumes (acoustically noisy). In addition, computer software was used to determine the source and location of the acoustic event.

Full-text PDF of this report is available for free download from: http://www.virginiadot.org/vtrc/main/online_reports/pdf/10-r24.pdf

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Research and Technology Implementation Office

September 2010

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Research Digest Item 15 Development of Safety Performance Functions for Two-Lane Roads Maintained by the Virginia Department of Transportation : Final Report VIRGINIA TRANSPORTATION RESEARCH COUNCIL (VTRC) VTRC 10-R25 • 2010 In recent years, significant effort and money have been invested to enhance highway safety. As available funds decrease, the allocation of resources for safety improvement projects must yield the maximum possible return on investment. Identifying highway locations that have the highest potential for crash reduction with the implementation of effective safety countermeasures is therefore an important first step in achieving the maximum return on safety investment.

This study was undertaken to develop safety performance functions (SPFs) for use in Virginia in conjunction with SafetyAnalyst™, a computerized analytical tool that can be used for prioritizing safety projects. A safety performance function is a mathematical relationship (model) between frequency of crashes by severity and the most significant causal factors of crashes for a specific type of road. Although the SafetyAnalyst User’s Manual recommends four SPFs for two-lane segments, these SPFs were developed using data from Ohio. Because the transferability of these SPFs to other states could not be guaranteed by the developers of the four recommended SPFs, it is necessary to calibrate or develop valid SPFs for each state using appropriate data from the state.

Full-text PDF of this report is available for free download from: http://www.virginiadot.org/vtrc/main/online_reports/pdf/10-r25.pdf

Item 16 An Examination of Practices for Retrofitting Existing Roads with Sidewalks in the United States VIRGINIA TRANSPORTATION RESEARCH COUNCIL (VTRC) VTRC 10-R4 • 2010 In Virginia, as in the United States, many roads were built without sidewalks. With steadily increasing efforts to develop a more balanced, multimodal transportation system, missing sidewalks pose a unique connectivity issue.

Although the Virginia Department of Transportation’s (VDOT) Policy for Integrating Bicycle and Pedestrian Accommodations allows for the construction of bicycle and pedestrian facilities separate from highway construction, it does not specifically address the issue of missing sidewalks. The purpose of this study was to identify and examine current practices relating to retrofitting existing roads with sidewalks in order to provide VDOT with guidance on addressing the issue of missing sidewalks in its transportation system.

Three tasks were performed to achieve the study objectives. First, a literature review was conducted to identify material that addressed issues relating to retrofitting existing roads with sidewalks. Second, VDOT’s current practices were documented and reviewed based on a survey and interviews of district staff. Third, the practices of state departments of transportation (DOTs) and selected localities were identified based on a survey of the DOT and locality representatives, the literature review, and a search of agency websites.

Full-text PDF of this report is available for free download from: http://www.virginiadot.org/vtrc/main/online_reports/pdf/10-r4.pdf

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Research and Technology Implementation Office

September 2010

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Research Digest Item 17 Investigation of the Rolling Wheel Deflectometer As a Network-Level Pavement Structural Evaluation Tool VIRGINIA TRANSPORTATION RESEARCH COUNCIL (VTRC) VTRC 10-R5 • 2010 The Virginia Department of Transportation (VDOT) currently uses the results of automated surface distress surveys to assist in developing pavement maintenance strategies for its interstate and primary roadways. Totaling nearly 27,000 lane-miles, these roadways consist of flexible, rigid, and composite (flexible over rigid) pavements. These video-based surface distress data consist of quantities of distress that are visible in the pavement surface.

Obtaining structural data from falling weight deflectometer (FWD) testing has only recently been implemented at the network level. A growing area of interest in pavements research is developing new and faster technologies that are well suited for nondestructively assessing the pavement structure without causing delays to the traveling public. One recently developed system, the rolling wheel deflectometer (RWD), measures the response from onehalf of an 18-kip single-axle load traveling at normal highway speeds. This technology can measure deflections for approximately 200 to 300 lane-miles per day, which is approximately 10 times the production of traditionally used FWD testing. The primary advantages of using RWD are two-fold: the testing can be conducted at highway speeds for increased safety, and the loading by the RWD is thought to replicate better the actual dynamic effects on pavements caused by heavy vehicle loading. A potential application might be to use the RWD to pre-screen the pavement network to identify areas where more detailed investigations are needed (e.g. by traditional FWD testing).

This report provides the results of RWD testing on three Virginia routes and a comparison of the deflection results obtained with RWD and FWD testing on sections of I-64 and I-81. The RWD provided deflection measurements over long distances at or near highway speeds with minimal interruption to the highway users, and the RWD and FWD deflection results were not well correlated. Further, the standard deviation of the RWD deflection results fluctuated with changes in surface mix type. For these reasons, the study recommends that VDOT not pursue additional RWD testing on roadways that are expected to have low deflection values and are likely to be uniform in structural cross-section (i.e. conditions that might be expected on interstate facilities).

Full-text PDF of this report is available for free download from: http://www.virginiadot.org/vtrc/main/online_reports/pdf/10-R5.pdf

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Research and Technology Implementation Office

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Research Digest Item 18 Investigation of Fiber-Reinforced Self-Consolidating Concrete VIRGINIA TRANSPORTATION RESEARCH COUNCIL (VTRC) VTRC 10-R8 • 2010 The rising cost of materials and labor, as well as the demand for faster construction, has prompted development of cheaper, faster alternatives to conventional building techniques. Self-consolidating concrete (SCC), a high performance concrete characterized by its ability to flow without segregation under its own weight, promises to speed construction while reducing the need for skilled labor. However, experience has shown that SCC may be prone to shrinkage cracking, which may compromise its durability. In conventional concrete, fiber reinforcement has been used to control cracking and increase tensile and flexural strength.

This study evaluated the feasibility of fiber-reinforced SCC (FR-SCC) for structural applications.

Full-text PDF of this report is available for free download from: http://www.virginiadot.org/vtrc/main/online_reports/pdf/10-r8.pdf

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Research and Technology Implementation Office

September 2010

Page 14