Technical Reports (VTTI)

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  • Feasibility Study for Animal Detection Driver Warning Systems on Corridor Q/Route 460
    Bell, Stephen; Crowder, Tarah; Alden, Andrew S. (2024-03)
    Corridor Q, as part of the Appalachian Development Highway System, is a 14-mile-long addition to US-460 in Buchanan County, Virginia that is currently under construction. The diverse large- and medium-sized wildlife in this area present risks for drivers, requiring an exploration of the different animal-vehicle crash (AVC) mitigation technologies available to state departments of transportation (DOTs). In addition to the wildlife typically found in the area, which already poses a threat to drivers (and vice versa), a local herd of elk was reintroduced to this area between 2012 and 2014 and are often seen along this new roadway. Elk pose additional dangers due to their large body size, herding behavior, and many other unique qualities that set them apart from other similar local species, like white-tailed deer. Elk primarily feed on low-growing vegetation such as the grasses typically used during construction to prevent roadside erosion. Soon after construction began, the elk were observed feeding on the grass along Corridor Q and tended to remain in the area. GPS collar data from tagged elk near Corridor Q reflect this observation. AVCs involving elk are costly, averaging around $73,196 in 2020 US dollars, with more recent estimates of $80,771. AVC mitigation efforts along Corridor Q must consider the unique challenges elk will present to drivers upon completion of the roadway. While many different AVC mitigation techniques are in use today, this project focuses on the feasibility of utilizing animal detection and driver warning systems (AD/DWS) as a cost-effective measure to reduce the risk of AVCs along Corridor Q. AD/DWS combine animal detection (AD) with driver warning (DW) systems to effectively alert drivers of animals near the roadway. ADS are electronic systems that use methods such as tracking motion via camera, thermal imagery, or radar, the breaking of an invisible beam, or perturbation of underground sensors, with the goal of detecting the presence of an animal near the roadway. DWS are signage systems, connected to ADS, that give drivers advanced alerts of animal detection locations. In this study, the Virginia Tech Transportation Institute researched the state of AD/DWS technologies to determine the feasibility for their use on Corridor Q, to review products that are currently available to state DOTs as off-the-shelf solutions, and to identify potential locations for a pilot study site. Interviews with subject matter experts were conducted to help guide this research. To ensure a cost-effective approach, an analysis of the partially completed portion of the roadway, and the activity of the local elk population, was conducted to observe the varying characteristics that could distinguish between areas of higher potential risk of elk-vehicle crashes (EVCs) versus areas of lower risk. In doing so, implementation of AD/DWS can be focused on the areas of higher apparent risk, keeping overall costs down while maximizing the effectiveness of these systems. AD/DWS were considered both as standalone options and in combination with other strategies to assess which method is better. As this is a new roadway, typical analysis methods used for assessing AVC mitigation strategies, such as historic crash data and traffic volume data, could not be applied. Some elk in the area were collared with GPS tracking devices, allowing for an analysis of their movement around and near the roadway. Additionally, the Virginia DOT (VDOT) provided as-built data of the new roadway, and georeferenced footage was recorded to assist with the analysis. Ultimately, the roadway was classified into distinct sections where conditions were indicative of a higher risk of EVCs based on an analysis of the data collected for this project. Details on these sections were provided to three vendors with different potential AD/DWS products that VDOT could readily purchase. These vendors provided their assessments and costs of implementing their solutions along Corridor Q.
  • AI Dash Cam Performance Benchmark Testing
    Camden, Matthew C.; Soccolich, Susan A.; Ridgeway, Christie; Parks, R. Lucas; Hanowski, Richard J. (2023-06-30)
    The objective of this project was to benchmark the performance of three driver monitoring systems (DMSs): Motive DC-54, Samsara HW-CM32, and Lytx DriveCam SF400. The study was conducted in two phases. Phase One was an assessment to benchmark the performance of the three DMSs. This phase involved testing the ability of each system to successfully capture and alert unsafe driver behavior. Phase Two of the study, the user performance benchmarking phase, acquired feedback from heavy vehicle drivers regarding various attributes of each system’s quality. One hundred eighty-eight (188) CMV drivers with an active commercial driver’s license (CDL-A) participated in the survey.
  • Implementation and Evaluation of a Buried Cable Animal Detection System and Deer Warning Sign
    Druta, Cristian; Alden, Andrew S. (Virginia Transportation Research Council, 2019-05)
    Animal-vehicle collisions (AVC), and deer-vehicle collisions (DVC) in particular, are a major safety problem on Virginia roads. Mitigation measures such as improved fencing and location-specific driver alerts are being implemented and evaluated in Virginia and elsewhere. One of the most promising mitigation methods uses a buried cable animal detection system (BCADS) to provide roadside or in-vehicle warnings to approaching drivers based on the active presence of an animal on or near the roadway. BCADS may also be deployed in combination with exposure controls such as fencing to provide monitored, at- grade, animal crossing zones where conventional passages (e.g. culverts and bridges) are unavailable. In this study, the Virginia Department of Transportation (VDOT) in collaboration with the Virginia Tech Transportation Institute (VTTI) implemented and monitored the performance of a BCADS on a public road to provide a real-world assessment of system capabilities and possible operation issues. The BCADS has proved effective and reliable in a previous evaluation performed under more controlled and secure conditions at the Virginia Smart Road facility in Blacksburg, VA. A BCADS was installed on State Route 8 in the town of Christiansburg, VA on a road segment known to have a relatively high rate of DVCs. The system identified crossings of large- and medium-sized animals and provided data on their location along the length of the sensing cable. The BCADS and associated surveillance and communications equipment were powered by a solar photovoltaic system. A cellular modem provided for remote system monitoring and data collection. A flashing light “Deer Crossing” warning sign was installed at the site and was wirelessly linked with the BCADS to alert approaching drivers when an animal crossing was detected. Continuous BCADS and all-weather video surveillance data were collected during an 11-month period (November 2017–September 2018) to monitor animal movement, vehicle traffic, and system performance. Data on driver response to the activated warning sign during the dawn and dusk hours were collected in two separate daily sessions within a 3-month period. Study findings indicate that the BCADS is capable of detecting larger animals such as deer, and sometimes smaller animals such as coyotes, with approximately 99% reliability. The system also performed well when covered by approximately 60 cm (2 ft.) of snow. Moreover, the system was tested under various vehicle traffic conditions, and rare instances of relatively minor interferences were observed. Vehicle speed and brake light application data collected during warning sign activation showed that approximately 80% of drivers either braked or slowed in response, indicating that the sign was effective.
  • Full-Scale Laboratory Evaluation of Hybrid Composite Beams for Implementation in a Virginia Bridge
    Moen, Cristopher D.; Roberts-Wollmann, Carin L.; Cousins, Thomas E. (Virginia Transportation Research Council, 2018-08)
    This research project studied a steel-reinforced concrete and fiber-reinforced polymer (FRP) structural element called the Hybrid-Composite Beam (HCB). The beam was used in a skewed simple span superstructure replacement project over the Tides Mill Stream in Colonial Beach, Virginia. For typical HCB construction, each beam is transported to site as a lightweight FRP beam shell. Self-consolidating concrete is pumped into the shell interior arch form, and when the concrete hardens, it stiffens and strengthens the beam so that it can act as falsework to carry the weight of a cast-in-place concrete bridge deck. Unstressed prestressing strands are embedded in the FRP shell bottom flange during the resin placement, and these strands equilibrate thrust in the arch and stiffen the beam to meet service deflection criteria. After the deck is placed, the HCB system performs as a longitudinal flexural member, with the bridge deck resisting compression and prestressing strands and the FRP bottom flange resisting tension. The primary research goal was to document the HCB as a structural component and as a bridge system, with the outcome being validation of key assumptions that can be applied to future designs such as, for example, strain compatibility between the FRP shell and steel strands. The research was conducted in five phases. In Phase 1, the HCB flexural rigidity and through-depth strain distributions were quantified considering just the FRP shell with unstressed strands. These tests confirmed flexural rigidity estimated by hand calculations and strain compatibility under uniform loads. Phase 2 evaluated flexural behavior of the HCB FRP shell and poured concrete arch. Phase 3 testing was performed after three HCBs were made integral with cast-in-place concrete end diaphragms and a reinforced concrete bridge deck. Point loads, to simulate an HL-93 design truck as specified in American Association of State Highway and Transportation Officials (AASHTO) LFRD Bridge Design Specifications, were applied to the bridge deck to maximize shear, flexure, and torsion in the skewed bridge. Live load distribution between the three girders was approximately equal and the assumption of strain compatibility between the bridge deck, FRP shell, and steel strand was confirmed. Stresses in bottom flange FRP strands and the top of deck concrete were less than 30% of material limits under service level live loads. The concrete arch fell below the composite neutral axis, placing it in tension along the span. After the live load system tests, a more detailed investigation was performed in Phase 4 to explore transverse deck behavior. Transverse flexural demands were approximately 20% of the design capacity and standard truss bars, as specified by the Virginia Department of Transportation, are not necessary because of the small clear span of the slab between beams. In Phase 5, the bridge system was saw-cut longitudinally to separate it into three individual HCB composite beams. Two beams were load tested to failure at the Structures Laboratory at Virginia Tech. For one of the two beams tested at Virginia Tech, 14 out of a total 22 strands were cut at mid-span to simulate strand deterioration and for comparison the other beam remained undamaged prior to testing. The observed beam failure modes were mid-span concrete crushing for the undamaged beam and mid-span strand-FRP bond failure for the damaged beam. In support of Phase 5, a three-dimensional (3D) finite element model was developed to explore flexural and shear force distributions along the span, which led to a shear design procedure in which shear force is distributed based on the relative moments of inertia of the FRP shell and arch. Shear resistance is provided by the FRP shell webs and the concrete arch and fin.
  • Implementation of a Precast Inverted T-Beam System in Virginia: Part II: Analytic and Field Investigations
    Menkulasi, Fatmir; Cousins, Thomas E.; Roberts-Wollmann, Carin L. (Virginia Transportation Research Council, 2018-08)
    The inverted T-beam superstructure is a bridge system that provides an accelerated construction alternative for short-to-medium-span bridges. The system consists of adjacent precast inverted T-beams with a cast-in-place concrete topping. This bridge system is expected to not experience the reflective cracking problems manifested in short-to-medium-span bridges constructed with traditional adjacent voided slab or adjacent box beams. This report presents the results of three phases of a comprehensive research project to develop and implement an inverted T-beam system for Virginia. The three phases are: investigation of time-dependent and temperature effects, investigation of end zone stresses, and live load testing. The first investigation is of time-dependent effects in composite bridges with precast inverted T-beams. The analysis was performed for a two-span continuous bridge. An analytical study was performed to quantify the stresses generated as a result of differential shrinkage, creep and temperature gradient at various sections in both directions. At the cross-sectional level, an elastic sectional analysis approach using the age-adjusted effective modulus method was used to perform the investigation. At the structure level, the effects of uniform temperature changes, thermal gradients and differential shrinkage and creep were investigated and quantified in terms of axial restraint forces and restraint moments. It is shown that, by paying attention to detailing and by selecting a mix design for the cast-in-place topping that has relatively low shrinkage and high creep, the potential for excessive cracking can be reduced. The second investigation is of the stresses in the end zones of such a uniquely shaped precast element. The transfer of prestressing force creates vertical and horizontal tensile stresses in the end zones of the beam. A series of three-dimensional (3D) finite element analyses were performed to investigate the magnitude of these tensile stresses. Various methods of modeling the prestressing force, including the modeling of the transfer length, were examined and the effect of notches at the ends of the precast beams was explored. Existing design methods were evaluated; strut-and-tie models, calibrated to match the results of 3D finite element analyses, are proposed as alternatives to existing methods to aid designers in sizing reinforcing in the end zones. The final section reports the results of live load testing performed on the first inverted T-beam bridge in Virginia on U.S. 360 over the Chickahominy River. A finite element model of Phase I of the U.S. 360 Bridge was created and the live load distribution factors were analytically determined. Live load tests using a stationary truck were performed on Phase I of the U.S. 360 Bridge with the purpose of quantifying live load distribution factors and validating the results from the finite element analyses. It is concluded that it is appropriate to estimate live load distribution factors using AASHTO provisions for cast-in-place slab span bridges.
  • Evaluation of Innovative Approaches to Curve Delineation for Two-Lane Rural Roads
    Gibbons, Ronald B.; Flintsch, Alejandra Medina; Williams, Brian M.; Li, Yingfeng; Machiani, Sahar Ghanipoor; Bhagavathula, Rajaram (Virginia Transportation Research Council, 2018-06)
    Run-off-road crashes are a major problem for rural roads. These roads tend to be unlit, and drivers may have difficulty seeing or correctly predicting the curvature of horizontal curves. This leads to vehicles entering horizontal curves at speeds that are too high, which can often lead to vehicles running off the roadway. This study was designed to examine the effectiveness of a variety of active and passive curve warning and curve delineation systems on two two-lane rural roads to determine which is the most effective at reducing vehicle speeds and assisting lane-keeping. The study consisted of a human-factors study, as well as an observational study. There were nine curves examined in the study on two road sections in Southwest Virginia. The human-factors study included participants whose speed and lane position were tracked as they drove through eight curves, both before and after new treatments were installed in each of the eight curves. The observational study examined the speed and lane position of traffic on all the curves before and after the installation of the new treatments. The observational study included a curve on a road near the primary study section. The results of the study were mixed, with every tested system leading to some reductions in speed or encroachments at some parts of the curve while also leading to increases in the same values at other parts of the curve. No clear difference was discovered between passive and active systems or between delineation and warning systems. The study recommends that in addition to a safety assessment, specific curve characteristics and budget should be the main considerations in the selection of a treatment for a curve.
  • Carbon Fiber Reinforced Polymer Grids for Shear and End Zone Reinforcement in Bridge Beams
    Ward, John; Magee, Mitch; Roberts-Wollmann, Carin L.; Cousins, Thomas E. (Virginia Transportation Research Council, 2018-01)
    Corrosion of reinforcing steel reduces life spans of bridges throughout the United States; therefore, using non-corroding carbon fiber reinforced polymer (CFRP) reinforcement is seen as a way to increase service life. The use of CFRP as the flexural reinforcement in bridge girders has been extensively studied. However, CFRP transverse reinforcement has not been investigated as rigorously, and many of those studies have focused on carbon fiber composite cable (CFCC) stirrups. The use of C-Grid or NEFMAC grid as options for transverse reinforcing has not been previously investigated. This testing program first determined the mechanical properties of C-Grid and NEFMAC grid and their respective development lengths. Five 18-ft long, 19-in deep beams were fabricated to test the C-Grid and NEFMAC, as well as conventional steel and CFCC stirrups. The beams were loaded with a single point load closer to one end of the beam to create a larger shear load for a given moment. Overall beam displacement was measured, and beams were fitted with rosettes and instrumentation to capture initiation of shear cracking. Test results were compared to theoretical shear capacities calculated using four different methods. The design method which provided the best prediction of shear strength was the AASHTO modified compression field theory, using equations for β and θ. The manufacturer’s guaranteed tensile strength should be used for design, as long as that strength is the average strength, as determined by at least five tests, reduced by three standard deviations. Shear cracks were controlled to a similar width as in beams with steel stirrups when at least two layers of grid were in place. An additional study was undertaken to determine if CFRP grids, either alone or in combination with traditional steel stirrups, could be used to control cracking in the end zones of pretensioned I-beams. Unfortunately, it was determined that, due to its low modulus, the amount of CFRP grid required to control cracking in the end zones was not economically feasible. Nevertheless, this study concluded that C-Grid and NEFMAC grid are both viable shear reinforcement options outside of the end regions. This report presents the initial recommendations for design.
  • Linear Cracking in Bridge Decks
    Balakumaran, Soundar S.G.; Weyers, Richard E.; Brown, Michael C. (Virginia Transportation Research Council, 2018-03)
    Concrete cracking in bridge decks remains an important issue relative to deck durability. Cracks can allow increased penetration of chlorides, which can result in premature corrosion of the reinforcing steel and subsequent spalling of the concrete deck. Although it is understood that the service life of bridge decks is affected by concrete cracking, the degree to which cracking affects service life is unknown. Crack repairs may be expensive, and only a few state transportation agencies have developed effective decision-making tools to support engineering decisions about whether and how to repair cracks in bridges. To understand how various factors affect the formation of cracks and to comprehend how cracks influence the performance of bridge decks, a comprehensive literature review was performed of publications from the early 1970s to the present. With findings from more than 45 years of research, the influences of about 30 factors were included in the literature review. In this study, 37 highway bridges in Virginia were selected on the basis of environmental exposure, geographic location, traffic conditions, and construction era. Ten decks with ordinary portland cement (OPC) concrete with a water–cementitious material (w/c) ratio of 0.47 with uncoated reinforcement were built from 1968 through 1971, and 27 decks with concrete with a w/c ratio of 0.45 with epoxy-coated reinforcement were built from 1984 through 1991. Of the newer 27 decks, 11 had concrete with supplementary cementitious material (SCM) such as fly ash and slag. The study included field surveys, sampling, and extensive data collection with regard to the decks. In addition, a laboratory study of the collected samples was conducted to understand the material properties and to determine the chloride contents. Statistical methods were used to analyze the collected data and to form regression models for prediction of crack influence on chloride diffusion. The increase in chloride diffusion through cracks when compared to that of corresponding uncracked locations was statistically significant. No strong correlation was found between surface crack width and chloride diffusion; however, a significant correlation was found between crack depth and chloride diffusion. To understand the effects of cracks on the durability of the structures, service life was estimated using a probabilistic chloride diffusion model based on Fick’s second law of diffusion. The estimated service life of the decks with concrete with SCM was around 100 years but only if no cracks were present. The presence of cracks affected the service life significantly. With higher crack frequencies, the service life plunged to the levels of decks built with OPC concrete, which was significantly lower to begin with. The service life of decks built with OPC concrete was not significantly affected by the presence of cracks, primarily because the high permeability of OPC concrete, with or without the presence of cracks, results in a shorter service life for OPC concrete decks. Time to corrosion initiation for corrosion-resistant reinforcing bars, ASTM A1035 (VDOT Class I reinforcement) and ASTM A955 (VDOT Class III reinforcement), was estimated, and the service lives were much longer compared to those of the decks in this study constructed with other types of reinforcement. Implementation guidance for quality assurance of newly built bridge decks with modern concrete mixtures and corrosion-resistant reinforcement and for maintenance of existing bridge decks was developed based on the study results.
  • Analysis of Repeated Network-Level Testing by the Falling Weight Deflectometer on I-81 in the Virginia Department of Transportation's Bristol District
    Bryce, James M.; Katicha, Samer W.; Diefenderfer, Brian K.; Flintsch, Gerardo W. (Virginia Transportation Research Council, 2016-11)
    This study was undertaken in an effort to determine the required time between subsequent rounds of network-level pavement deflection testing using a falling weight deflectometer (FWD) on the Virginia Department of Transportation’s (VDOT’s) interstate system. Network-level deflection testing was conducted in two separate years (2006 and 2011) on Interstate 81 in VDOT’s Bristol District. The testing was conducted using the FWD at an interval of 0.2 miles in the right-hand lane (travel lane) of the interstate. The objective of this study was to analyze the results from the 2011 testing and compare them to the results obtained from the 2006 study to determine if the previously completed FWD survey of VDOT’s entire interstate network needed to be repeated. First, deflection values that were obtained from pavement segments that received treatments between the two sets of tests were identified and omitted from any comparison. Second, the two datasets were compared directly (i.e., without accounting for errors) and were modeled to account for the expected errors in the data defined as the root mean square of the difference between 2006 and 2011 measurements. The results of the 2011 testing showed lesser deflection and greater structural number values when compared to the data collected in 2006. A characterization of the errors implicit in each set of measurement showed that the errors outweigh the changes in deflection values from the two datasets. Therefore, it was not possible to quantify a recommended time between subsequent rounds of deflection testing on the pavement network. Since the literature shows significant benefits to conducting pavement deflection testing on the network, VDOT will continue this practice based on local needs and as budgetary constraints allow.
  • Examination of the Current Practice of Lighting in Virginia: Nighttime Work Zones and Improving Safety Through the Development of Nighttime Lighting Specifications
    Bhagavathula, Rajaram; Gibbons, Ronald B.; Medina, Alejandra; Terry, Travis N. (Virginia Transportation Research Council, 2017-09)
    This project evaluated current nighttime work zone lighting practices for limited-access highways and primary routes in Virginia through (1) an on-site evaluation of lighting levels in work zones; (2) an illuminance characterization of various commercially available light towers; and (3) a human factors evaluation of those light towers and developed effective nighttime work zone lighting requirements for Virginia. The majority of the static nighttime work zones used metal halide portable light towers. Mobile operations such as milling and paving used equipment-mounted balloon lights and LEDs. Horizontal illuminance levels in the work zones were affected by the number of light towers, locations of the light towers, and number of traffic lanes in the work zone. The measured horizontal illuminance levels in the work zones were much higher than recommended levels. Milling and paving operations that used equipment-mounted lights had lower illuminance levels than operations that used portable light towers. Vertical illuminance levels in the traffic lane were significantly affected by the aiming of the luminaires on the portable light towers. Luminaires aimed into the traffic travel lane produced higher vertical illuminance levels, which can result in disability and discomfort glare and consequently reduce visibility. The visual performance of drivers in a work zone can be influenced by the type and orientation of the light tower. An orientation aimed toward the driver resulted in lowering drivers’ visual performance, both objectively and subjectively. This decrease in visual performance could be attributed to higher vertical illuminance. To increase the drivers’ visual performance and reduce glare in the work zone, efforts should be taken to aim the light towers in an active nighttime work zone away from the direction of traffic or perpendicular to it. In these orientations, all the three light towers tested had similar visual performance measures. The increase in the mean vertical illuminance level in the critical range is associated with higher perceived ratings of glare. Results showed that the mean vertical illuminance in the distance range of 260 to 65 ft to the light tower could be used as an objective measure of glare. A mean vertical illuminance of less than 17 lux resulted in lower perceived glare ratings. Results also indicated that light towers should be oriented so that the angle between the beam axis and driver line-of-sight axis is always greater than or equal to 90 degrees. Finally, a draft specification outline including a plan for on-site lighting evaluation of a work zone is presented.
  • Assessment of the Performance of Light-Emitting Diode Roadway Lighting Technology
    Gibbons, Ronald B.; Li, Yingfeng; Meyer, Jason E. (Virginia Transportation Research Council, 2015-10)
    This study, championed by the Virginia Department of Transportation (VDOT) Traffic Engineering Division, involved a thorough investigation of light-emitting diode (LED) roadway lighting technology by testing six types of roadway luminaires (including housing and all components enclosed) in a laboratory environment and on the field over a 2-year period. The results showed that LED luminaires exhibited superior lighting and related qualities compared to high-pressure sodium luminaires. Different photometric characteristics were found among LED luminaires of different designs, indicating a careful selection considering light distribution and illuminance level is necessary for individual lighting applications. During the first 2 years of operation, the average light loss for the LED luminaires was 6% based on laboratory testing. The study also found that implementing LED technology systematically will result in a return on investment between 3.25 and 5.76 for different scenarios over a 25-year period due to savings in maintenance and energy consumption. The study resulted in the VDOT LED Roadway Luminaire Specification document and developed recommendations relevant to VDOT’s implementation of LED technology.
  • Continuous Friction Measurement Equipment As a Tool for Improving Crash Rate Prediction: A Pilot Study
    de León Izeppi, Edgar; Katicha, Samer W.; Flintsch, Gerardo W.; McCarthy, Ross; McGhee, Kevin K. (Virginia Transportation Research Council, 2016-01)
    A comprehensive pavement management system includes a Pavement Friction Management Program (PFMP) to ensure pavement surfaces are designed, constructed, and maintained to minimize friction-related crashes in a costeffective manner. The Federal Highway Administration’s (FHWA) Technical Advisory 5040.38 on Pavement Friction Management supersedes a previous advisory that focused on skid crash reduction. In addition to traditional locked-wheel friction-testing devices, this new advisory recommends continuous friction measuring equipment (CFME) as an appropriate method for evaluating pavements. The study described in this report developed a pavement friction inventory for a single construction district in Virginia using the Grip Tester, a low-cost CFME. The continuous friction data were then coupled with crash records to develop a strategy for network analysis that could use friction to improve the ability to predict crash rates. The crash rate analysis applied the well-established methodology suggested by the FHWA for the identification of high crash risk areas using safety performance functions (SPFs), which include empirical Bayes rate estimation from observed crashes. The current Virginia Department of Transportation SPF models were modified to include skid resistance and radius of curvature (interstate and primary system only) to improve the predictive power of the models. A variation of the same methodology was also used to contrast the effect of two different friction repair treatments, i.e., conventional asphalt overlay and high friction surface treatments, to explore how their strategic use can impact network level crash rates. The result suggests significant crash reductions with comprehensive economic savings of $100 million or more when applied to a single relatively rural district. These findings easily justify an aggressive state-level PFMP and further support continued research to quantify the influence of other pavement-related characteristics such as macrotexture, grade, and cross-slope.
  • Evaluation of a Buried Cable Roadside Animal Detection System
    Druta, Cristian; Alden, Andrew S. (Virginia Transportation Research Council, 2015-06)
    Animal-vehicle collisions (AVC) are a concern for departments of transportation as they translate into hundreds of human fatalities and billions of dollars in property damage each year. A recently published report states that the Virginia Department of Transportation (VDOT) currently spends over $4 million yearly to remove about 55,000 deer carcasses from its roadways. Currently, one of the most effective existing methods to reduce AVCs is the use of animal detection systems, which can detect animals near the roadway and alert approaching drivers accordingly. In order to reduce AVCs in Virginia, VDOT, in collaboration with the Virginia Tech Transportation Institute, proposed the evaluation of an innovative roadside animal detection system in naturalistic and controlled conditions. This type of system offers numerous apparent advantages over above-ground animal detection technologies when environmental interferences, such as precipitation and vegetation, and site-specific characteristics, such as topology, subsidence, and road curvature, are considered. The subject animal detection system (ADS), a 300-m-long buried dual-cable sensor, detects the crossing of large and medium-sized animals and provides data on their location along the length of the cable. The system has a central processor unit for control and communication and generates an invisible electromagnetic detection field around buried cables. When the detection field is perturbed, an alarm is declared and the location of the intrusion is determined. Target animals are detected based on their conductivity, size, and movement, with multiple simultaneous intrusions being detected during a crossing event. The system was installed and tested at a highly suitable site on the Virginia Smart Road where large wild animals, including deer and bear, are often observed in a roadside environment. This report describes the installation of the ADS, data collection and analysis methodology, evaluation of the system’s reliability and effectiveness, cost analysis, and implementation prospects. The system used continuous, all-weather and nighttime video surveillance to monitor animal movement and to gauge system detections, and potential non-detections of the ADS. Also, a communication link between the buried ADS and the Virginia Smart Road fiber optic network was established to allow operation and monitoring of the system from a dedicated server in the Virginia Smart Road Control Room. A performance verification of the network communication was successfully conducted through continuous data collection and transfer to a storage unit. Data were collected continuously for a period of 10 months that included winter, and then analyzed to determine overall detection performance of the system. Data analyses indicate that the ADS, if properly installed and calibrated, is capable of detecting animals such as deer and bear, and possibly smaller animals, such as fox and coyotes, with over 95% reliability. The ADS also performed well even when covered by 3 ft of snow. Moreover, the system was tested under various traffic conditions and no vehicle interferences were noted during the same monitoring period. The acquired data can be used to improve highway safety through driver warning systems installed along roadway sections where high wildlife activity has been observed. Additionally, this system may be integrated with the connected vehicle framework to provide advance, in-vehicle warnings to motorists approaching locations where animals have been detected in or near the roadway.
  • Evaluation of the MMLS3 for Accelerated Wearing of Asphalt Pavement Mixtures Containing Carbonate Aggregates
    Druta, Cristian; Wang, Linbing; Lane, D. Stephen (Virginia Transportation Research Council, 2014-06)
    The purpose of this study was to develop an accelerated wearing protocol for assessing the susceptibility of asphalt surface mixtures to polishing. This was the second phase of the study. The first phase focused on assessing the characteristics of selected carbonate aggregates available in Virginia that are normally classified as “polishing” and thus not considered suitable for use in pavements except for those roads with an average daily traffic of less than 750 vehicles per day. The selection of aggregates used in pavements is critical in producing surfaces that will continue to provide good skid resistance through a lengthy service life. The specifications of the Virginia Department of Transportation (VDOT) call for “non-polishing aggregate” for use in most surface layers. The study was aimed at making use of locally available polishing aggregates that can reduce the cost of asphalt mixtures while maintaining satisfactory wearing and skid characteristics of the pavements. The objectives of the research were (1) to evaluate the polishing/wear features of mixtures containing limestone aggregate in the laboratory using an accelerated method; (2) to compare friction properties of the laboratory-polished specimens with actual pavement friction measurements; and (3) to compare friction properties of mixtures containing carbonate rock or blends with those of mixtures with non-carbonate rocks. The study included three types of aggregates, i.e., limestone, quartzite, and granite, and blends of these aggregates. The surface mixtures studied were conventional SM-9.5 and SM-12.5 mixtures containing various percentages of limestone, limestone recycled asphalt pavement, and limestone-granite/quartzite blends. The suggested test protocol to evaluate the polishing of asphalt concrete specimens prepared in the laboratory was developed using the third-scale model mobile load simulator (MMLS3). The MMLS3 is capable of applying realistic rolling wheel contact stresses similar to those on highways from the moving traffic. The skid resistance, friction, and texture of actual pavement surfaces and laboratory-fabricated specimens were measured after different polishing intervals. Skid resistance and frictional characteristics were measured by the British pendulum tester, dynamic friction tester, and locked-wheel skid tester; the circular texture meter was used to measure surface macrotexture. Results showed that the MMLS3 can be used to simulate traffic wearing of asphalt concrete specimens of different shapes and sizes in the laboratory including core specimens removed from existing pavements and that the BPT is effective in characterizing changes in friction on specimens that are subjected to simulated trafficking via the MMLS3. Further, test specimens should have a high initial macrotexture and mixtures should have good stability so that the wearing effects are focused on the aggregates. The study recommends that the Virginia Center for Transportation Innovation and Research (VCTIR) work with Virginia Tech and VDOT’s western districts to design and conduct an experiment to explore a series of carbonate / non-carbonate aggregate blends for asphalt mixtures and that the mixture gradations be designed to prevent the absence of macrotexture from impacting the ability to measure the “polish” of the coarse aggregate structure of the experimental mixtures. VCTIR should purchase tires with different tread patterns and try them on the MMLS3 to evaluate the polishing rate of specimens in more detail.
  • Best Practices and Performance Assessment for Preventative Maintenance Treatments for Virginia Pavements
    de León Izeppi, Edgar; Morrison, Akyiaa; Flintsch, Gerardo W.; McGhee, Kevin K. (Virginia Transportation Research Council, 2015-08)
    Preventive maintenance has the potential to improve network condition by retarding future pavement deterioration. This report outlines guidelines for implementing a preventive maintenance policy for bituminous pavements. Preventive maintenance treatments currently being used in Virginia include chip seal, slurry seal, microsurfacing, and thin hot mix asphalt overlays. Historical pavement condition data were obtained from the Virginia Department of Transportation’s Pavement Management System for these treatments, and treatment performance models were developed. A district-level treatment selection tool was developed to facilitate the district-level decision-making process. A prioritized list of pavement sections was generated, maximizing the cost-effectiveness of the selected treatments subject to budgetary constraints set by the Central Office. As a pilot implementation, the treatment selection tool was then run for each pavement classification in each district. The results of this pilot suggest that this selection tool has the potential to be a practical decision support tool.
  • Safety, Operational, and Energy Impacts of In-vehicle Adaptive Stop Displays Using Connected Vehicle Technology
    Noble, Alexandria M. (Connected Vehicle/Infrastructure University Transportation Center (CVI-UTC), 2015-07-30)
    Un-signalized intersections create multiple opportunities for missed or misunderstood information. Stop sign-controlled intersections have also been shown to be a source of delay and emissions due to their frequent, often inappropriate use. By using connected vehicle technology, it is possible to place electronic stop signs at more conspicuous locations that can communicate with the in-vehicle systems. Then, if a conflict is imminent at an intersection, the vehicle’s system alerts the driver, thus reducing the probability of missed information, as well as decreasing the amount of unnecessary delay, fuel consumption, and emissions by only prompting a stop when a conflict is present. Before implementing any new technology, it is important to assess it from both a transportation engineering and human factors standpoint to determine the value of such a system. The objective of this study was to assess perceived benefits of an adaptive in-vehicle stop display and to determine if there were any negative safety implications with the use of this system. This was accomplished through a test track experiment with 49 participants. These drivers were presented with a standard R1-1 stop sign on the in-vehicle display, as well as an experimental sign, which informed them to proceed through the intersection with caution. Results indicate the implementation of this technology reduces delay, decreases fuel consumption, and does not instigate any safety decrements.
  • Description of the SHRP 2 Naturalistic Database and the Crash, Near-Crash, and Baseline Data Sets
    Hankey, Jonathan M.; Perez, Miguel A.; McClafferty, Julie A. (Virginia Tech Transportation Institute, 2016-04)
    The focus of this project was to identify and prepare crash, near-crash, and baseline data sets extracted from the Second Strategic Highway Research Program (SHRP 2) Naturalistic Driving Study (NDS) trip files, then to make that information available to researchers for use in their analysis projects. A dozen trigger algorithms were executed on 5,512,900 trip files in the SHRP 2 NDS, and a manual validation of these algorithms identified 1,549 crashes and 2,705 near-crashes. A longitudinal deceleration-based algorithm produced the highest percentage of valid crashes and near-crashes. Baselines were selected via a random sample stratified by participant and proportion of time driven. Triggered epochs and the resulting crashes and near-crashes were reviewed and analyzed by a large team of data reductionists and quality control coordinators following a rigorous training, testing, and monitoring protocol. As a result, 20,000 baselines, including all drivers in the SHRP 2 NDS, were prepared and are recommended for researchers using a case-cohort design. An additional 12,586 baselines are also available for researchers who may require more power in their analyses but are able to forego a fully proportional representation of all drivers in the study. Researchers using this data set are encouraged to review the data dictionaries on the InSight website prior to doing analysis and to be particularly careful in selecting the best subset of crashes, near-crashes, and baselines that informs their research questions.
  • Identification of Consented Driver Trips in the SHRP 2 Naturalistic Driving Study Data Set
    McClafferty, Julie A.; Perez, Miguel A.; Hankey, Jonathan M. (Virginia Tech Transportation Institute, 2015-02)
    The Second Strategic Highway Research Program (SHRP 2) Naturalistic Driving Study (NDS) data set contains approximately 5.51 million naturalistic driving trip files across thousands of consented drivers, making it the largest data set of its kind. Before these data can be used to answer research questions, we need to ensure that only consented driver data will be used and that non-consented data are removed from the database. Virginia Tech Transportation Institute (VTTI) research staff performed a Rapid Driver Identification (RDI) task to identify trip files with and without consented drivers. An initial driver recognition step was performed on a small sample of files from each vehicle, followed by a review of the full data set using a recently developed rapid assessment tool that permitted files to be reviewed approximately 25 times faster than before. In all, 6.48 million files were coded, of which 5.51 million are associated with a consented driver during a consented time period. These files represent 3,353 vehicles and 3,546 unique participants, of which 3,241 were primary drivers and 305 were secondary drivers. The products of this task will serve future researchers using the SHRP 2 NDS website for years to come, as well as provide tools and expertise for the rapid assessment of Driver ID in future large-scale naturalistic driving studies.
  • Infrastructure Pavement Assessment & Management Applications Enabled by the Connected Vehicles Environment – Proof-of-Concept
    Flintsch, Gerardo W.; Smith, Brian L. (Research and Innovative Technology Administration, 2015-09-30)
    The objective of this project was to develop prototypes and conduct a field test of system level applications of a connected vehicle pavement condition measurement system. This allowed the research team to: (1) investigate different approaches to a connected vehicle pavement measurement system; and (2) determine the optimum procedures for collecting, processing, aggregating, and storing the data to support engineering and management decisions. The study found that roughness measures obtained from probe vehicles are comparable to roughness measures obtained from the profile, when the appropriate parameters that affect roughness were taken into account. A sensitivity analysis suggested that data sampling and quarter-car parameters were the most critical parameters. Finally, the results of the network-level simulations showed that the probe vehicle vertical acceleration measurements (collected from a mobile smart phone application) have the potential to be used for network-level prescreening of deficient pavement sections.
  • Automated Vehicle Crash Rate Comparison Using Naturalistic Data
    Blanco, Myra; Atwood, Jon; Russell, Sheldon M.; Trimble, Tammy E.; McClafferty, Julie A.; Perez, Miguel A. (Virginia Tech Transportation Institute, 2016-01-08)
    This study assessed driving risk for the United States nationally and for the Google Self-Driving Car project. Driving safety on public roads was examined in three ways. The total crash rates for the Self-Driving Car and the national population were compared to (1) rates reported to the police, (2) crash rates for different types of roadways, and (3) scenarios that give rise to unreported crashes. First, crash rates from the Google Self-Driving Car project per million miles driven, broken down by severity level were calculated. The Self-Driving Car rates were compared to rates developed using national databases which draw upon police-reported crashes and rates estimated from the Second Strategic Highway Research Program (SHRP 2) Naturalistic Driving Study (NDS). Second, SHRP 2 NDS data were used to calculate crash rates for three levels of crash severity on different types of roads, broken down by the speed limit and geographic classification (termed “locality” in the study; e.g., urban road, interstate). Third, SHRP 2 NDS data were again used to describe various scenarios related to crashes with no known police report. This analysis considered whether such factors as driver distraction or impairment were involved, or whether these crashes involved rear-end collisions or road departures. Crashes within the SHRP 2 NDS dataset were ranked according to severity for the referenced event/incident type(s) based on the magnitude of vehicle dynamics (e.g., high Delta-V or acceleration), the presumed amount of property damage (less than or greater than $1,500, airbag deployment), knowledge of human injuries (often unknown in this dataset), and the level of risk posed to the drivers and other road users (Antin, et al., 2015; Table 1). Google Self-Driving Car crashes were also analyzed using the methods developed for the SHRP 2 NDS in order to determine crash severity levels and fault (using these methods, none of the vehicles operating in autonomous mode were deemed at fault in crashes).