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Browsing by Author "Flintsch, Alejandra Medina"

Now showing 1 - 9 of 9
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    Access Control Design on Highway Interchanges
    Rakha, Hesham A.; Flintsch, Alejandra Medina; Arafeh, Mazen; Abdel-Salam, Abdel-Salam Gomaa; Dua, Dhruv; Abbas, Montasir M. (Virginia Center for Transportation Innovation and Research, 2008-01-01)
    The adequate spacing and design of access to crossroads in the vicinity of freeway ramps are critical to the safety and traffic operations of both the freeway and the crossroad. The research presented in this report develops a methodology to evaluate the safety impact of different access road spacing standards. The results clearly demonstrate the shortcomings of the AASHTO standards and the benefits of enhancing them. The models developed as part of this research were used to compute the crash rate associated with alternative section spacing. The study demonstrates that the models satisfied the statistical requirements and provide reasonable crash estimates. The results demonstrate an eight-fold decrease in the crash rate when the access road spacing increases from 0 to 300 m. An increase in the minimum spacing from 90 m (300 ft) to 180 m (600 ft) results in a 50 percent reduction in the crash rate. The models were used to develop lookup tables that quantify the impact of access road spacing on the expected number of crashes per unit distance. The tables demonstrate a decrease in the crash rate as the access road spacing increases. An attempt was made to quantify the safety cost of alternative access road spacing using a weighted average crash cost. The weighted average crash cost was computed considering that 0.6, 34.8, and 64.6 percent of the crashes were fatal, injury, and property damage crashes, respectively. These proportions were generated from the field observed data. The cost of each of these crashes was provided by VDOT as $3,760,000, $48,200, and $6,500 for fatal, injury, and property damage crashes, respectively. This provided an average weighted crash cost of $43,533. This average cost was multiplied by the number of crashes per mile to compute the cost associated with different access spacing scenarios. These costs can assist policy makers in quantifying the trade-offs of different access management regulations.
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    Active and Adaptive Roadway Delineation Systems
    Williams, Brian M.; Gibbons, Ronald B.; Flintsch, Alejandra Medina (National Surface Transportation Safety Center for Excellence, 2017-10-13)
    Heavy fog presents a significant safety hazard to drivers by reducing their ability to see the roadway and other vehicles. Even so, drivers often fail to adjust their speed to account for the reduced visibility, resulting in stopping distances that exceed visibility distance. Active delineators, or in-pavement light emitting diode (LED) markers, are an emerging technology which can be used to assist drivers in traveling through fog-prone areas by marking road or lane boundaries. However, there is a lack of research indicating how the presence of active delineators might also affect a driver’s behavior. This study sought to examine how the presence of active delineators in fog might affect drivers’ speed. Three lighting patterns and two brightness levels were tested. In daytime conditions, the delineators had no effect on speed. During nighttime conditions, participants often drove faster when the active delineators were present. Participants felt that the active delineators were helpful for navigating through the fog in both daytime and nighttime conditions, but preferred the higher brightness settings in the daytime.
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    Assessment of a Drowsy Driver Warning System for Heavy Vehicle Drivers: Final Report
    Olson, Rebecca Lynn; Morgan, Justin F.; Hanowski, Richard J.; Daily, Brian; Zimmermann, Richard P.; Blanco, Myra; Bocanegra, Joseph L.; Fitch, Gregory M.; Flintsch, Alejandra Medina (United States. National Highway Traffic Safety Administration, 2008)
    Drowsiness has a globally negative impact on performance, slowing reaction time, decreasing situational awareness, and impairing judgment. A field operational test of an early prototype Drowsy Driver Warning System was conducted as a result of 12 years of field and laboratory studies by the National Highway Traffic Administration and the Federal Motor Carrier Safety Administration. This project included Control and Test groups. The final data set for the analysis consisted of 102 drivers from 3 for-hire trucking fleets using 46 instrumented trucks. Fifty-seven drivers were line-haul and 45 were long-haul operators. The data set contained nearly 12.4 terabytes of truck instrumentation data, kinematic data, and video recordings for 2.4 million miles of driving and 48,000 driving-data hours recorded, resulting in the largest data set ever collected by the U.S. Department of Transportation. In this study, 53 research questions were addressed related to safety benefits, acceptance, and deployment. Novel data reduction procedures and data analyses were used. Results showed that drivers in the Test Group were less drowsy. Drivers with favoring opinions of the system tended to have an increase in safety benefits. Results of the assessment revealed that the early prototype device had an overall positive impact on driver safety.
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    Countermeasures to Reduce Truck-Mounted Attenuator (TMA) Crashes: A State-of-the-Art Review
    Mosunmola Aroke, Olugbemi; Sylvester Onuchukwu, Ikechukwu; Esmaeili, Behzad; Flintsch, Alejandra Medina (MDPI, 2022-05-09)
    To support worker and driver safety, this study conducted a comprehensive literature review to identify methods of enhancing TMA visibility, improving work zone configurations, and ensuring worker safety. To increase TMA recognition, this study observed that the use of a 6-to-8-inch wide yellow and black inverted ‘V’ pattern of retroreflective chevron markings, sloped at a 45-degree angle downward in both directions from the upper center of a rear panel is effective in alerting drivers to work zones. This study also recommends applying amber and white warning LEDs, which flash in an asynchronous pattern at a 1 Hz frequency and are mounted against a solid-colored background for a 360-degree view visible at least 1500 feet from the work zone. In addition, a work zone vehicle configuration consisting of a lead, buffer, and advance warning truck with a buffer space between 100 and 150 ft is suggested to reduce the risk of lateral intrusions and TMA roll-ahead. In parallel, workers should wear high-visibility vests noticeable at a minimum distance of 1000 feet and headwear with at least 10 square inches of retroreflective material. Some intelligent transport systems are also suggested to enhance TMA recognition and potentially minimize work zone fatalities. Application of the recommended guidelines will potentially improve current practices and significantly reduce the occurrence of TMA crashes in construction and maintenance work zones.
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    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.
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    Integrating the Adaptive Lighting Database with SHRP 2 Naturalistic Driving Data
    Li, Yingfeng; Gibbons, Ronald B.; Flintsch, Alejandra Medina (National Surface Transportation Safety Center for Excellence, 2015-09-16)
    This report details efforts to integrate the Adaptive Lighting Database (ALD) with the Second Strategic Highway Research Program (SHRP 2) Naturalistic Driving Study (NDS) and the Roadway Information Database. The ALD provides detailed in situ lighting performance data and associated safety, traffic, and roadway data for seven states: Washington (WA), North Carolina (NC), California (CA), Delaware (DE), Minnesota (MN), Vermont (VT), and Virginia (VA). The SHRP 2 database provides naturalistic driving data from a large-scale study carried out at six sites around the nation: Bloomington, Indiana; central Pennsylvania; Tampa Bay, Florida; Buffalo, New York; Durham, North Carolina; and Seattle, Washington. The RID, which was developed as part of the SHRP 2 program, provides detailed traffic and roadway information for the SHRP 2 sites. The integration of these datasets would make it possible for researchers to investigate relationships between different lighting characteristics, roadway configurations, and roadway safety. With this objective in mind, the research team developed an in-depth description of the NDS database structure, data elements, and database relationships; documented in detail the data entities, format, and content of the ALD; and developed and demonstrated two Geographic Information System (GIS) approaches for integrating NDS and ALD data. The two GIS approaches target different needs and requirements. The first approach involved data integration directly between the ALD and NDS time series data. By matching both lighting and time series data points onto the same roadway network, simple spatial joins or linear referencing mechanisms could be used to relate individual points from both datasets. The approach involved both existing and custom tools developed on the ArcGIS platform. Data in both databases could then be integrated through spatial and relational joins. The researchers used data for the State of Washington to demonstrate the approach and associated advantages and challenges. Time series data representing approximately 2,800 nighttime NDS trips were matched to the ALD roadway network. The second approach involved data integration of the ALD and NDS data based on the roadway segments in the RID. Within the NDS database, time series data points were matched to a digital map of the roadway network defined by links (uniquely identified by a LINKID), directly isolating time series data on the links of interest and eliminating the need for additional spatial processing. The RID roadway network was then matched with the ALD roadway network and each ALD roadway segment was assigned the LINKID of the corresponding RID roadway segment, allowing relational database joins to be used, which are many orders of magnitude faster than spatial joins. To demonstrate this approach, the research team used a draft version of the RID roadway data and lighting data for the State of North Carolina.
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    Linear Regression Crash Prediction Models : Issues and Proposed Solutions
    Rakha, Hesham A.; Arafeh, Mohamadreza; Abdel-Salam, Abdel-Salam Gomaa; Guo, Feng; Flintsch, Alejandra Medina (Virginia Tech. Virginia Tech Transportation Institute, 2010-05)
    The paper develops a linear regression model approach that can be applied to crash data to predict vehicle crashes. The proposed approach involves novice data aggregation to satisfy linear regression assumptions namely error structure normality and homoscedasticity. The proposed approach is tested and validated using data from 186 access road sections in the state of Virginia. The approach is demonstrated to produce crash predictions consistent with traditional negative binomial and zero inflated negative binomial general linear models. It should be noted however that further testing of the approach on other crash datasets is required to further validate the approach.
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    Onboard Safety Systems Effectiveness Evaluation: Final Report
    Hickman, Jeffrey S.; Guo, Feng; Camden, Matthew C.; Flintsch, Alejandra Medina; Hanowski, Richard J.; Mabry, J. Erin (United States. Federal Motor Carrier Safety Administration, 2013-10)
    The purpose of this project was to conduct a retrospective effectiveness evaluation study on three commonly deployed onboard safety system (OBSS) types using previous data acquired directly from participating motor carriers. These OBSS technologies included lane departure warning (LDW), roll stability control (RSC), and forward collision warning (FCW) systems. The current study assessed the effectiveness of these three different OBSS types installed on Class 7 and 8 trucks as they operated in their normal revenue-producing routes. Although the crash data were acquired from 14 carriers representing small, medium, and large carriers hauling a variety of commodities (including a total of 88,112 carrier crash records-- USDOT-reportable accidents as well as minor incidents-- and 151,624 truck-years of operation that represented 13 billion miles traveled), the dataset in the current study was skewed toward larger, for-hire carriers and may not fully represent the overall U.S. trucking population. The benefit-cost analyses clearly showed the estimated benefits of LDW and RSC systems deployed at participating fleets outweighed the estimated costs. The analysis of the fleet crash data using the same methodology did not show a statistically significant difference in FCW-related crash occurrence rates between vehicles with or without an FCW system installed. Retrospectively, this result is primarily attributed to the lack of sufficient data (in terms of number of trucks with a deployed FCW system in the dataset) to be able to detect safety benefits with statistical significance at the observed level. Focus groups were also conducted with drivers and safety managers who had experience with LDW, RSC, or FCW systems. Drivers' and safety managers' opinions and perceptions of each OBSS type were generally very positive.
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    Supporting CMV Driver Distraction Outreach Efforts: Letter Report Summary
    Morgan, Justin F.; Flintsch, Alejandra Medina; Blanco, Myra; Hanowski, Richard J.; Fitchett, Vikki L.; Fitzgerald, Hollie E.; Radlbeck, Joshua (National Surface Transportation Safety Center for Excellence, 2015-04-08)
    The Federal Motor Carrier Safety Administration (FMCSA) CMV Driving Tips website (https://cms.fmcsa.dot.gov/safety/driver-safety/cmv-driving-tips-overview) is a source for information on safety and practical driving tips for CMV drivers and safety managers. The purpose of this project was to review the driver distraction content on the CMV Driving Tips site and identify recently published research that may be included in a potential site update. The content was made more accessible to a broad audience of CMV drivers by simplifying the text, providing a Spanish-language translation, and creating English and Spanish versions of a one-page tip sheet on how to reduce distracted driving.