Virginia Tech Transportation Institute (VTTI)

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Development of models for detection of automobile driver impairment
Dingus, Thomas A. (Virginia Tech, 1985-08-05)
Two of the leading causes of automobile accidents are driver impairment due to alcohol and drowsiness. Apparently, a relatively large percentage of these accidents occur because drivers are unaware of the degree to which they are impaired due to these sources. The purpose of this research was to develop models which could detect driver impairment due to alcohol, drowsiness, or the combination of alcohol and drowsiness, and which could be practically implemented in an automobile. Such detection models, if successfully implemented in conjunction with a system to warn an impaired driver of his or her condition, could potentially save hundreds of lives each year. Six driver-subjects operated a computer controlled driving simulator during each of four conditions. The four conditions consisted of a control condition, an alcohol condition, a sleep-deprived condition, and a combination alcohol and sleep-deprived condition. Moderate levels of alcohol and sleep deprivation were used for this study. Nineteen performance and behavioral measures were collected during this study. Each measure was evaluated singly and in combination with other measures to determine potential value for detection of driver impairment. Detection models were then formulated using the most promising detection measures. The results indicated that a useful on-board drowsiness impairment detection device is possible and practical for highway driving. This device would also, in all likelihood, provide useful detection information regardless of whether low to moderate amounts of alcohol were present in a drowsy driver. The results also showed that on-board alcohol impairment detection may be possible at moderate to high BAC.
Attentional demand evaluation for an automobile moving-map navigation system
Dingus, Thomas A. (Virginia Tech, 1987)
A study was undertaken to test and evaluate the human factors design aspects of an automobile moving-map navigation system. The primary objective of the study was to assess the driver attentional demand required by the navigation system during vehicle operation. A secondary objective of the study was to assess design specifics and determine whether or not the design was optimal in terms of efficiency of use in an automotive environment. Thirty-two driver-subjects drove a specially instrumented 1985 Cadillac Sedan de Ville on public roadways for this research. A cross-section of driver-subjects (both genders, ages 18 to 73, and driving experience from 2,000 to 40,000 miles per year) participated, and a cross·section of roadway types (residential, two-lane state route, and limited·access four-lane) and traffic conditions (light and moderate) were used as part of this research. The driver-subjects were asked to perform a variety of tasks while operating the research vehicle. These tasks included navigation tasks normally performed while using the navigation system, as well as a wide variety of conventional automotive tasks (e.g., tuning the radio or reading the speedometer) normally performed during vehicle operation. The purpose of asking the driver-subjects to perform a variety of conventional automotive tasks was so that direct comparisons in attentional demand could be made between tasks performed daily in an automotive environment and the navigation tasks. Twenty-one performance and behavioral measures were collected and analyzed for this research. These measures included eye—scanning and dwell-time measures, task-completion-time measures, and a variety of measures indicating driver performance and behavior. The data analyses for these measures focused on two major goals. First, the analyses determined which tasks (both navigator and conventional) required the highest attentional demand. Second, the analyses were used to determine groups of tasks which, for all practical purposes, required equivalent attentional demand. The results of the analyses indicated that the navigation system is a relatively effective device, useful for its intended purpose. The results also indicated that a number of design improvements are required, however, to optimize the safety and efficiency of the device. An iterative process of design improvement and further research into the effects of improved design on required attentional demand is therefore recommended.
Development of Human Factors Guidelines for ATIS and CVO Identify Strengths and Weaknesses of Alternative Information Display Formats
Hulse, Melissa C.; Dingus, Thomas A.; Mollenhauer, Michael A.; Liu, Y. C.; Jahns, Steven K.; Brown, T.; McKinney, B. (United States. Federal Highway Administration, 1993-10)
This report is one of a series produced as part of a contract designed to develop precise, detailed, human factors design guidelines for Advanced Traveler Information Systems (ATIS) and Commercial Vehicle Operations (CVO). The goals of the work covered in this report were to: (1) identify information format alternatives for ATIS devices for both private drivers and CVO applications, and (2) identify research issues that must be addressed in order to develop effective information format guidelines. To achieve these goals, and to make the greatest progress possible toward the ultimate project goal of guideline development, the project developed the strategy of turning the current state of knowledge into tools applicable to any ATIS design. Four primary design-decision tools were developed. These tools are intended to help either professional or nonprofessional human factors designers make appropriate tradeoff decisions in designing effective ATIS displays. The four tools are: (1) Sensory Modality Allocation, (2) Trip Status Allocation, (3) Display Format Allocation, and (4) Display Location.
TravTek Evaluation Task C3 - Camera Car Study
Dingus, Thomas A.; McGehee, Daniel V.; Hulse, Melissa C.; Jahns, Steven K.; Manakkal, N.; Mollenhauer, Michael A.; Fleischman, Rebecca N. (United States. Federal Highway Administration, 1995-06)
The goal of the TravTek Camera Car Study was to furnish a detailed evaluation of driving and navigation performance, system usability, and safety for the TravTek system. To achieve this goal, an instrumented "camera car" was developed to provide comprehensive driving performance and behavior measurement capability. Six navigation test configurations were evaluated in the camera car study. These included: TravTek route-map display, TravTek route-map display with supplementary voice guidance. . TravTek symbolic guidance-map display. . TravTek symbolic guidance-map display with supplementary voice guidance. . Paper map. . Paper textual direction list. A primary finding of this research was that turn-by-turn guidance information (whether presented verbally, in a textual list or by a graphic display) enhances the performance, usability, and/or safety when compared with alternatives which provide holistic route information. For this study, the TravTek turn-by-turn with voice condition and a paper direction list (with a large legible font and similar in layout to a computer generated list found at some rental-car counters) provided the best overall performance. The TravTek turn-by turn without voice and route-map with voice conditions were comparable in many respects to these conditions, but did not perform as well with respect to driving performance and safety-related driver error. In contrast, the TravTek route-map without voice had the greatest overall impact on the driving task and was the least safe of all the navigation conditions tested. However, these safety differences are mitigated by user experience, and by driver selection of other available options (as shown in other TravTek studies). The paper map control condition was the least usable means of navigation in the study and resulted in substantially worse navigation performance than any other condition.
Review and evaluation of models that produce trip tables from ground counts
Sivanandan, R.; Narayanan, Arvind; Lei, Peng (Virginia Center for Transportation Innovation and Research, 1996-02)
This research effort was motivated by the desires of planning agencies to seek alternative methods of deriving current or base year Origin-Destination (O-D) trip tables without adopting conventional O-D surveys that are expensive, time consuming and labor intensive. This study had two objectives: (t) to conduct a review of existing approaches and models that produce trip tables from ground counts, and to select a few models for testing and evaluation, and (2) to perform a detailed testing of selected models based on application to both hypothetical and real networks, and to conduct performance evaluation and sensitivity analyses of these models. Two models, namely, The Highway Emulator (THE), and the Linear Programming (LP) model developed at Virginia Tech, were chosen for comprehensive testing and evaluation. For test purposes, these two models were applied to the following three case studies: (1) Sample Network, (2) Purdue University Network, and (3) Pulaski Town Network. While the first network was a hypothetical one, the other two were real networks. Different cases of targetable information and combinations of percentage available target cells and link volume information were used in the tests. These tests enabled a comprehensive evaluation of the performance and sensitivity analyses of the models. The test results were judged by two criteria: (1) the closeness of the model output tables to the "correct" or "surveyed" tables, and (2) the replication of observed link volumes by the models. The test results led to the following key conclusions: In general, the LP model results have proven to be superior, both in terms of closeness of modeled trip tables to the "correct"/"surveyed" tables, and in terms of replicating observed link volumes, for all the case studies, The exception to this is the structural target case, when THE produced better results, in terms of closeness of output tables to the "correct "l" surveyed" tables. This is based on the assumption that the "correct"/"surveyed" trip tables used for the case studies were in fact "correct"/"true". 2. THE model performed superior to the LP model for the structural target case (almost all the cases), where the target contains 1/0 cell values, 1 for those cells which represent O-D Interchanges that are feasible, and 0 for those that are not. This has practical implications in that if a region does not have a prior table available as target, then a structural target could be used.A word of caution must be noted with regard to conclusion # 2 above. While one would be tempted to use THE with a structural target for applications where a prior table is not available, it must be noted that the modeled results of both THE and LP turned out to be poor when compared with the "correct"/"surveyed" tables for all the cases, even though THE results were better than those of LP. However, these conclusions are based on tests on specific and limited number of networks, and under the assumption that the data used in testing and evaluation were accurate enough. The adoptability of these models and the use of one model versus the other must be decided based on the above facts, and in the context of error rates reported in this study, However, this study has highlighted the value of using such theoretical models for trip table estimation without performing conventional surveys.
Development of Human Factors Guidelines for Advanced Traveler Information Systems and Commercial Vehicle Operations: Literature Review
Dingus, Thomas A.; Hulse, Melissa C.; Jahns, Steven K.; Alves-Foss, J.; Confer, S.; Rice, A.; Roberts, I.; Hanowski, Richard J.; Sorenson, D. (United States. Federal Highway Administration, 1996-11)
The purpose of Task A was to conduct a literature review of human factors-applicable articles associated with Advanced Traveler Information Systems (ATIS) and ATIS-related commercial vehicle operations (CVO) systems. Specifically, Task A was to assess existing human factors guidelines to determine their applicability to ATIS systems and identify research gaps that would be filled to establish complete and comprehensive ATIS guidelines. As with any literature review, the conduct of Task A was treated as a foundation for subsequent tasks. The duration of Task A (3 months) was such that some of the literature of interest could not be obtained prior to publication of this document. Thus, the literature review does not, in effect, end with this report.
Application of Magnetorheological Dampers for Vehicle Seat Suspensions
Reichert, Brian Anthony Jr. (Virginia Tech, 1997-12-03)
This study evaluates and provides solutions to the problem of poor subjective feel of seat suspensions that employ magnetorheological (MR) dampers and skyhook control. An Isringhausen seat suspension that had been modified to replace the stock passive damper with a controllable MR damper was used to evaluate the problems and potential solutions. A seat suspension tester was built using materials from 80/20 Incorporated and a hydraulic actuation system from MTS. An HP Dynamic Signal Analyzer was used as the main piece of data acquisition equipment, along with a Pentium PC and National Instruments Data Acquisition card. All of the hardware is installed in a controlled laboratory facility at Virginia Tech's Advanced Vehicle Dynamics Lab. The first task was to analyze the source of the unexpected peak in the acceleration spectrum of the suspended seat. This analysis was accomplished using a combination of pure tone inputs and a Fourier analysis of a simple model of the system. This analysis indicated that the peak is actually three times the resonant frequency of the seat suspension. The analysis also indicates that the frequency components continue at odd multiples of the resonant frequency, however, the third peak is the most noticeable. The third multiple is in the resonant frequency range (4-8 Hz) of the human body, so it was initially blamed for the poor subjective feel of the seat. However, solutions to remove this harmonic were tested without success. The work progressed to a time domain analysis, which eventually led to determining the source of the poor subjective feel. The seat suspension was excited with a variety of inputs. The seat acceleration and damper control current were examined in the time domain to show that the cause of the poor subjective feel is the control signal discontinuities. The control policy was modified to remove the control signal discontinuities and was found to improve the subjective feel of the seat. Finally, several two-degree-of-freedom control policies were implemented and tested. Although the results from this testing are inconclusive, they generated several recommendations for future research.
On-line Traffic Signalization using Robust Feedback Control
Yu, Tungsheng (Virginia Tech, 1997-12-18)
The traffic signal affects the life of virtually everyone every day. The effectiveness of signal systems can reduce the incidence of delays, stops, fuel consumption, emission of pollutants, and accidents. The problems related to rapid growth in traffic congestion call for more effective traffic signalization using robust feedback control methodology. Online traffic-responsive signalization is based on real-time traffic conditions and selects cycle, split, phase, and offset for the intersection according to detector data. A robust traffic feedback control begins with assembling traffic demands, traffic facility supply, and feedback control law for the existing traffic operating environment. This information serves the input to the traffic control process which in turn provides an output in terms of the desired performance under varying conditions. Traffic signalization belongs to a class of hybrid systems since the differential equations model the continuous behavior of the traffic flow dynamics and finite-state machines model the discrete state changes of the controller. A complicating aspect, due to the state-space constraint that queue lengths are necessarily nonnegative, is that the continuous-time system dynamics is actually the projection of a smooth system of ordinary differential equations. This also leads to discontinuities in the boundary dynamics of a sort common in queueing problems. The project is concerned with the design of a feedback controller to minimize accumulated queue lengths in the presence of unknown inflow disturbances at an isolated intersection and a traffic network with some signalized intersections. A dynamical system has finite L₂-gain if it is dissipative in some sense. Therefore, the H_infinity-control problem turns to designing a controller such that the resulting closed loop system is dissipative, and correspondingly there exists a storage function. The major contributions of this thesis include 1) to propose state space models for both isolated multi-phase intersections and a class of queueing networks; 2) to formulate H_infinity problems for the control systems with persistent disturbances; 3) to present the projection dynamics aspects of the problem to account for the constraints on the state variables; 4) formally to study this problem as a hybrid system; 5) to derive traffic-actuated feedback control laws for the multi-phase intersections. Though we have mathematically presented a robust feedback solution for the traffic signalization, there still remains some distance before the physical implementation. A robust adaptive control is an interesting research area for the future traffic signalization.
A Method to Enhance the Performance of Synthetic Origin-Destination (O-D) Trip Table Estimation Models
Sivanandan, R.; Nanda, Dhruv (Virginia Center for Transportation Innovation and Research, 1998-01)
The conventional methods of determining origin-destination (O-D) trip tables involve elaborate surveys, e.g., home interviews, that require considerable time, staff, and funds. To overcome this drawback, a number of theoretical models that synthesize O-D trip tables from link volume data have been developed. The focus of the research reported here was on two of these models The Highway Emulator (THE) and the Linear Programming (LP) model. These models use target/seed tables for guiding the development of output trip tables. In earlier research conducted by the Virginia Tech Center for Transportation Research for the Virginia Transportation Research Council, it was determined that the performance of these models could potentially be enhanced by using a superior target/seed table. The research in this report uses readily available socioeconomic data and link volume information to develop a methodology for obtaining an enhanced target/seed table through application of the trip generation and trip distribution steps of the four-step planning process. The enhanced table was then used as the target/seed to THE and LP models, and their performance evaluated. In addition to measuring the closeness of the output tables to surveyed tables and their capability to replicate observed volumes, their improvements over the case when a structural table is used as target was also studied. Tests showed that the use of the enhanced target/seed table significantly improved the performance of the LP model. However, mixed trends were obtained for THE.
Development of Human Factors Guidelines for Advanced Traveler Information Systems and Commercial Vehicle Operations: ATIS Function Transitions
Campbell, J. L.; Hanowski, Richard J.; Hooey, B. L.; Gore, B. F.; Kantowitz, Barry H. (United States. Federal Highway Administration, 1999-12)
The objective of the first experiment reported below was to measure the cognitive demands associated with transitioning across Advanced Traveler Information System (ATIS) functions. This required the development of both objective and subjective indices of driver behavior and cognition. To accomplish this, a small number of pre-drive trip scenarios that invoke appropriate transitions across ATIS functions were developed. Driving performance under more representative conditions was investigated in experiment 2 using a driving simulator. This study investigated several issues on the influence of an ATIS on driving behavior. The questions asked were: 1. How does a moving map display of the current vehicle location influence driving performance? 2. How do ATIS control inputs influence driving performance? Should they be allocated to pre-drive? Is it too much to expect the driver to do while in transit? 3. Do ATIS messages affect drivers' reactions to roadway events? 4. Does message potency affect drivers' reactions to roadway events? Overall, the two experiments reported here suggest that in-vehicle ATIS devices can be learned, understood, and successfully used by drivers for both pre-drive trip planning tasks and on-road driving conditions. ATIS devices have the potential to improve driver compliance to regulatory information, as compared with standard roadside signs. While concurrent visual and auditory ATIS alert messages may be beneficial, the visual ATIS messages alone are significantly better than roadside signage alone. While cognitive demands associated with ATIS transitions and ATIS complexity should continue to be a concern, these demands can be addressed by selecting ATIS functions with clear benefits to the driving task.
Development of Human Factors Guidelines for Advanced Traveler Information Systems and Commercial Vehicle Operations: Display Channels
Kantowitz, Barry H.; Hanowski, Richard J.; Garness, Sheila A. (United States. Federal Highway Administration, 1999-12)
Three experiments were conducted in a driving simulator to evaluate effects of in-vehicle message modality and message format on comprehension and memory for younger and older drivers. Visual icons and text messages were effective in terms of high comprehension and high memory retention over a 50-sec delay period for both older and younger drivers. Auditory icons (earcons) were unsuitable for older drivers, although younger drivers performed well using symbolic and speech in-vehicle messages. For visual only, auditory only, and auditory plus visual messages both textual and symbolic message formats were equally effective. No adverse effects of in-vehicle message presentation were found for lateral and longitudinal vehicle control. Implications of these findings for development of ATIS guidelines were discussed.
Effects of In-Vehicle Information Systems (IVIS) Tasks on the Information Processing Demands of a Commercial Vehicle Operations (CVO) Driver
Blanco, Myra (Virginia Tech, 1999-12-10)
This study was performed with two main goals in mind. The first goal was to understand and predict "red-lines" and "yellow-lines" in terms of what the CVO driver can process without hindering the primary task of driving. The second goal was to collect conventional secondary task data for CVO driving performance. An on-the-road experiment was performed with the help of 12 truck drivers. Type of task, presentation format, information density, and age were the independent variables used in the experiment. The 22 dependent measures collected were grouped into the following categories: eye glance measures, longitudinal driving performance, lateral driving performance, secondary task performance, and subjective assessment. The findings of this study strongly suggest that paragraphs should not be used under any circumstance to present information to the driver while the vehicle is in motion. On the other hand, the Graphics with Icons represent the most appropriate format in which driving instructions and information should be presented for IVIS/CVO tasks. In order to avoid a high visual attention demand to the driver due to a secondary task, only simple search tasks with the most important information shall be presented. Although the suggested format, type of task, and information density represent a higher visual attention demand than a conventional secondary task, these characteristics seem to bind a task with a moderate attentional demand. Other combinations of format, type of task, and information density will cause an increase in the driver's attentional demand that will consequently deteriorate their driving performance causing unsafe driving situations.
Phoenix Metropolitan Model Deployment Initiative Evaluation Report
Zimmerman, Carol A.; Marks, J.; Jenq, Jeffrey H.; Cluett, Chris; DeBlasio, Allan; Lappin, Jane; Rakha, Hesham A.; Wunderlich, Karl (United States. Federal Highway Administration, 2000-04)
This report presents the evaluation results of the Phoenix, Arizona Metropolitan Model Deployment Initiative (MMDI). The MMDI was a three-year program of the Intelligent Transportation Systems (ITS) Joint Program Office of the U.S. Department of Transportation. It focused on aggressive deployment of ITS at four sites across the United States, including the metropolitan areas of San Antonio, Seattle, NY/NJ/Connecticut as well as Phoenix. The focus of the deployments was on integration of existing ITS and deployment and integration of new ITS components. Nineteen public sector agencies and thirteen private firms participated in AZTech, the name given to the Phoenix MMDI. The evaluation encompassed fifteen AZTech projects. Eight projects provided advanced traveler information services; four projects were concerned with traffic management systems; and three deployed transit management systems. Traveler information services used public traffic and transit data from the central AZTech server along with data from the private sector. To address diverse market segments a wide range of dissemination technologies was used, including a personalized messaging system, Trailmaster Web site, commercialized Web page, Traffic Check Cable TV, in-vehicle navigation devices, Fastline personal communication device, transit status information, and travel information kiosks. AZTech's traffic management systems included eight "Smart Corridor" projects, three of which were included in the evaluation. Traffic management systems were deployed to provide interjurisdictional traffic signal coordination along major arterial roads in the region and to implement a computer-aided incident management system to facilitate efficiency and accuracy of incident investigations. Three transit management systems were deployed, all with automatic vehicle location technology to aid in dispatch and to provide status information to travelers. Integration among these various projects was a key feature of the AZTech program. The evaluation focused on six key study areas: network efficiency, safety, energy and emissions, customer satisfaction, costs of deployment, benefit/cost analysis, and institutional lessons. The intent was to evaluate changes in each of these areas brought about by deployment of new projects, as well as integration of both new and existing projects. This report presents the observed impacts of each of the fifteen MMDI projects and their integration and provides conclusions and recommendations based on the results.
Metropolitan Model Deployment Initiative San Antonio Evaluation Report
Carter, M.; Cluett, Chris; DeBlasio, Allan; Dion, Francois; Hicks, B.; Lappin, Jane; Novak, D.; Rakha, Hesham A.; St-Onge, C.; Van Aerde, Michael W. (United States. Department of Transportation, 2000-05)
This report presents the evaluation results of the San Antonio, Texas Metropolitan Model Deployment Initiative (MMDI). The MMDI was sponsored by the US Department of Transportation and focused on aggressive deployment of Intelligent Transportation Systems (ITS) at four sites, including San Antonio, Seattle, the New York/New Jersey/Connecticut metro area, and Phoenix. The general focus of the deployments was on the integration of existing ITS and the deployment of innovative traveler information projects. The San Antonio MMDI sought to make improvements in six key transportation goals. The first of these goals was the expansion and strengthening of the institutional framework necessary for successful ITS deployment and integration. The second goal was to improve traffic management through the expansion of the existing TransGuide freeway management system and the integration of a portion of that expanded system with a newly deployed arterial management system. The third goal of the San Antonio MMDI was to offer improved traveler information through enhancements to the existing TransGuide Web site and the deployment of 500 public agency in vehicle navigation units and 40 information kiosks. The fourth goal involved the deployment of train-sensing capabilities to provide integrated highway rail / traveler information system. The fifth goal focused on an emergency tele-medicine system linking ambulances in the field with receiving hospitals to provide superior emergency services. The final goal was to offer an integrated, area-wide database of real-time traffic conditions. This database is intended to fuse information from multiple sources in order to provide travel speeds for freeways and major arterials. The AVI tag component, which uses probe technology, was technically sound, but failed to attain significant market penetration to provide arterial travel times. This report focuses on the impact of these improvements in terms of system efficiency, safety, fuel consumption, customer satisfaction, cost effectiveness, and institutional impacts. Based on these metrics, the report concludes that the integration of ITS can offer substantial benefits, however, these benefits are not guaranteed. In order to maximize the opportunities for success, the report recommends undertaking a strategic approach and preparing to make a long-term commitment to ensure successful ITS deployment and integration.
The Impact of Local/Short Haul Operations on Driver Fatigue
Hanowski, Richard J. (Virginia Tech, 2000-05-23)
Massie, Blower, and Campbell (1997) indicate that trucks that operate less than 50 miles from the vehicle's home base comprise 58% of the trucking industry. However, despite being the largest segment, research involving local/short haul (L/SH) operations has been scant. In fact, little is known about the general safety issues in L/SH operations. As a precursor to the present research, Hanowski, Wierwille, Gellatly, Early, and Dingus (1998) conducted a series of focus groups in which L/SH drivers provided their perspective on safety issues, including fatigue, in their industry. As a follow-up to the Hanowski et al. work, the effort presented here consisted of an on-road field study where L/SH trucks were instrumented with data collection equipment. Two L/SH trucking companies and 42 L/SH drivers participated in this research. To the author's knowledge, this is the first in-situ data collection effort of its kind with L/SH drivers. The analyses focused on determining if fatigue is an issue in L/SH operations. Of primary interest were critical incidents (near-crashes) where drivers were judged to be at fault. The results of the analyses indicated that fatigue was present immediately prior to driver involvement in at-fault critical incidents. Though it is difficult to determine why fatigue was present, the results seem to indicate that much of the fatigue that the drivers' experienced was brought with them to the job, rather than being caused by the job. There are four basic outputs of the Phase II research: (1) a description of the L/SH drivers who participated, (2) a description of critical incidents, (3) a determination if fatigue is an issue in L/SH trucking, and (4) the validation of the fatigue factors cited in Hanowski et al. (1998) using a proposed fatigue model. These four outputs culminate in a set of pragmatic guidelines to address fatigue and other safety issues in L/SH operations. Five guidelines are proposed that are directed at: (1) driver education with regard to on-the-job drowsiness/inattention, (2) driver education with regard to sleep hygiene, (3) driver training, particularly for novice L/SH truck drivers, (4) driver screening, and (5) public monitoring of L/SH driver performance.
Improvement of Conspicuity of Trailblazing Signs: Phase III-Evaluation of Fluorescent Colors
Neale, Vicki L.; Anders, Richard L.; Schreiner, Christopher S.; Brich, Stephen C. (Virginia Center for Transportation Innovation and Research, 2001-02)
This report represents a Phase III effort to design and evaluate a new sign design for incident route trailblazing. The colors evaluated were fluorescent coral, fluorescent purple, fluorescent yellow-green, and non-fluorescent purple. The results indicate no significant differences in driving performance with regard to the four experimental sign color combinations. Regarding the subjective preference questionnaires, significant questionnaire results along with trend information suggest that black on fluorescent yellow green was the most preferred by younger and older drivers during both day and night visibility conditions. Nonetheless, this sign color has been assigned by FHWA for pedestrian, school, and bicycle crossings, which eliminated the opportunity to use fluorescent yellow-green as a unique sign color for trailblazing in incident management situations. Preference for non-fluorescent yellow on purple consistently increased at night when the sign became more luminant; however, the overall preference for this sign color combination was lower than for the other sign color combinations tested in this study. With the elimination of these two signs, the remaining contenders for a unique sign color combination were black on fluorescent coral and fluorescent yellow on fluorescent purple. Black on fluorescent coral was ranked significantly higher than fluorescent yellow on fluorescent purple for visibility and for overall preference. Questionnaire trend information suggests that black on fluorescent coral was more preferred than fluorescent yellow on fluorescent purple during daytime viewing conditions and less preferred than fluorescent yellow on fluorescent purple during nighttime viewing conditions. The overlay film used for the fluorescent coral sign was a first generation material that can reasonably be expected to result in improved nighttime luminance when produced in a full production run. In addition to the study results, drivers commented that the arrow on the sign was too small to determine directional information from a comfortable distance. Based on such driver comments, the research conclusions, and the federal regulations enacted since the outset of this series of experiments, the following recommendations are made: (1) black on fluorescent coral should be used as a unique incident management sign color, and (2) the directional arrow on the sign should be larger.
A Comparison of CORSIM and INTEGRATION for the Modeling of Stationary Bottlenecks
Crowther, Brent C. (Virginia Tech, 2001-05-09)
Though comparisons of simulation models have been conducted, few investigations have examined in detail the logical differences between models. If the output measures of effectiveness are to be interpreted correctly, it is important that the analyst understand some of the underlying logic and assumptions upon which the results are based. An understanding of model logic and its inherent effect on the results will aid the transportation analyst in the application and calibration of a simulation model. In this thesis, the car-following behavior of the CORSIM and INTEGRATION simulation models are examined in significant detail, and its impact on output results explained. In addition, the thesis presents a calibration procedure for the CORSIM sub-model, FRESIM. Currently, FRESIM is calibrated by ad hoc trial-and-error, or by utilizing empirically developed cross-referencing tables. The literature reveals that the relationship between the microscopic input parameters of the CORSIM model, and the macroscopic parameters of capacity is not understood. The thesis addresses this concern. Finally, the thesis compares the INTEGRATION and CORSIM models in freeway and urban environments. The comparison is unique in that the simulated networks were configured such that differences in results could be identified, isolated, and explained. Additionally, the simplified nature of the test networks allowed for the formulation of analytical solutions. The thesis begins by relating steady-state car-following behavior to macroscopic traffic stream models. This is done so that a calibration procedure for the FRESIM (Pipes) car-following model could be developed. The proposed calibration procedure offers an avenue to calibrate microscopic car-following behavior using macroscopic field measurements that can be easily obtained from loop detectors. The calibration procedure, while it does not overcome the inherent shortcomings of the Pipes model, does provide an opportunity to better calibrate the network FRESIM car-following sensitivity factor to existing roadway conditions. The thesis then reports an observed inconsistency in the link-specific car-following sensitivity factor of the FRESIM model. Because calibration of a network on a link-specific basis is key to an accurate network representation, a correction factor was developed that should be applied to the analytically calculated link-specific car-following sensitivity factor. The application of the correction factor resulted in observed saturation flow rates that were within 5% of the desired saturation flow rates. The thesis concludes with a comparison of the CORSIM and INTEGRATION models for transient conditions. As a result of the various intricacies and subtleties that are involved in transient behavior, the comparisons were conducted by running the models on simple networks where analytical solutions to the problem could be formulated. In urban environments, it was observed that the models are consistent in estimates of delay and travel time, and inconsistent in estimates of vehicle stops, stopped delay, fuel consumption, and emissions. Specifically, it was observed that the NETSIM model underestimates the number of vehicle stops in comparison with INTEGRATION and the analytical formulation. It was also observed that the NETSIM vehicles speed and acceleration profiles are characterized by abrupt accelerations and decelerations. These abrupt movements significantly impact stopped time delay and vehicle emissions estimates. Inconsistencies in emissions estimates can also be attributed to differences in the embedded rate tables of each model. In freeway environments for under-saturated conditions, INTEGRATION returned higher values of travel time and delay, and lower values of average speed than the FRESIM model. These results are consistent with the analytical solution, and can be attributed to the speed-flow relationship of each model. In saturated conditions, when the capacity of the bottleneck is equal to the demand volume, the emergent vehicle behavior of the FRESIM model was observed to be inconsistent with the analytical solution. The FRESIM vehicles were observed to dramatically decelerate upon entering a lower-capacity link. This deceleration behavior led to higher travel time and delay time estimates in FRESIM than in INTEGRATION. In over-saturated conditions, longer queue lengths were observed in FRESIM than in INTEGRATION, resulting in slightly higher travel and delay estimates in the FRESIM model. The reason for the discrepancy in queue lengths is unclear, as the network jam density in each model was equivalent.
Truck Modeling Along Grade Sections
Lucic, Ivana (Virginia Tech, 2001-05-11)
This research effort first characterizes the trucks traveling along US highways by analyzing data from Interstate 81. It is hypothesized that I-81 is typical of US highways and thus can provide some insight into typical truck characteristics. These truck characteristics are important for the development of an exhaustive vehicle performance procedure. Analysis was done based on data collected at the Troutville weigh station. The characterization involves an analysis of vehicle class distribution, GVW (Gross Vehicle Weight) distribution, vehicle volume distribution, Average Weight on Tractive Axle (AWTA), and typical weight-to-power ratios. The thesis then assembles a database of systematic field data that can be utilized for the validation of vehicle performance models. This database is unique because it was conducted in a controlled field environment where the vehicle is only constrained by its dynamics. Using the assembled field database, a simple constant power vehicle dynamics model for estimating maximum vehicle acceleration levels based on a vehicle's tractive effort and aerodynamic, rolling, and grade resistance forces was tested and validated. In addition, typical model input parameters for different vehicle, pavement, and tire characteristics are included in the thesis. The model was found to predict vehicle speeds at the conclusion of the travel along the section to within 5 km/h (3.1 mi/h) of field measurements, thus demonstrating the validity and applicability of the model. Finally, the research effort introduces the concept of variable power in order to enhance current state-of-the-art vehicle dynamics models and capture the build-up of power as a vehicle engages in gearshifts at low travel speeds. The proposed enhancement to the current state-of-practice vehicle dynamics model allows the model to reflect typical vehicle acceleration behavior more accurately. Subsequently, the model parameters are calibrated using field measurements along a test roadway facility.
Deploying an ITS Warning System for No-Passing Zones on Two-Lane Rural Roads
El Zarif, Jamal A. (Virginia Tech, 2001-06-28)
A new safety application, as part of ITS Advanced Rural Transportation System (ARTS), has been developed to be deployed on a two-lane rural road (Route 114), in Southwest Virginia. The route segment under study is subject to significant head-on accidents, as a result of two main conditions: 1- Illegal passing maneuvers crossing solid yellow line, and 2- A short passing sight distance due to the road vertical profile. The main objective of this research is to design a video detection-based warning system by installing an affordable and efficient system on the vertical crest curve on Route 114, capable of performing the following two main functions: 1.Detect vehicles that attempt to violate the no-passing zone restriction (i.e. when crossing into the opposing direction). 2.Warn the drivers violating the restriction in order to discourage them from continuing their maneuvers. System architecture as well as detailed system design was developed. A system simulation was conducted with the use of a special software program written with MATLAB. The simulation was applied for both "with" and "without" the system cases. The simulation runs showed that the system could virtually eliminate all head-on collisions, should violators obey the early warning messages displayed. Several sensitivity tests were made for different scenarios. Finally, the viability of the system was evaluated from economic point of view. The financial analysis revealed high economic indicators.
Impact of Sleeper Berth Usage on Driver Fatigue, Final Project Report
Dingus, Thomas A.; Neale, Vicki L.; Garness, Sheila A.; Hanowski, Richard J.; Keisler, Aysha S.; Lee, Suzanne E.; Perez, Miguel A.; Robinson, Gary S.; Belz, Steven M.; Casali, John G.; Pace-Schott, E. F.; Stickgold, Robert A.; Hobson, J. A. (United States. Federal Motor Carrier Safety Administration, 2002)
The goal of this project was to assess the impact that sleeper berth usage has on operator alertness. Forty-seven males and nine females participated in this study, constituting 13 teams and 30 single drivers. All drivers who participated in this study were recruited from one of four for-hire commercial trucking companies. Two tractors, a 1997 Volvo L4 VN-series tractor and a 1995 Peterbilt 379, with functionally identical instrumentation packages and data collection systems, were used for the study. The data acquisition system functioned to record four camera views, including the drivers face; driving performance information, including steering, lane departure, and braking; sleeper berth environmental data, including noise, vibration, and temperature; subjective alertness ratings; and data from the Nightcap sleep-monitoring system. The following results were obtained: (1) Sleeping in either a stationary or moving sleeper berth was shown to adversely affect sleep quality and quantity when compared to the home sleep data. This was particularly true for team drivers in moving trucks. (2) Team drivers generally acquired more sleep (greater than one hour per day on average) than did single drivers, with single drivers reporting six hours of sleep per 24-hour period and team drivers reporting just over seven hours per 24-hour period. (3) Team drivers had significantly more sleep disturbances than did single drivers. A primary cause of these disturbances appeared to be noise and vibration present in the sleeper berth of a moving truck. (4) In general, single drivers were rated as not drowsy more often and team drivers, who were rated as somewhat drowsy or moderately drowsy more often. However, of the 20 very/extremely drowsy episodes captured by Observer Ratings of Drowsiness, 16 were from single drivers. (5) Single drivers had many more critical incidents at all levels of severity relative to team drivers. (6) The frequency of critical incidents and driver errors varied significantly by the Hour of Day. However, many more incidents occurred during the afternoon and early evening as opposed to late at night. (7) Single drivers were more alert in the morning and gradually become fatigued during the day, whereas team drivers maintained a relatively constant level of alertness throughout the 24-hour clock.

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