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Federal Highway Administration Research and Technology
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The Highway Driving Simulator (HDS) is one of the research tools used at the Human Factors Laboratory for a variety of behavioral studies related to safety and operations conducted for Federal Highway Administration (FHWA) and other stakeholders. The simulator consists of a full automobile chassis surrounded by a semicircular projection screen. Five projectors render a seamless 240-degree view (motorists' field-of-view) of high-fidelity, computer-generated roadway scenes.
Located at FHWA’s research center in McLean, VA, the driving simulator is a high-fidelity, state-of-the-art research tool that the Human Factors Laboratory uses to generate multiple driving scenarios for evaluation and analysis.
In 2012, the simulator was upgraded to enhance the motion base, from 3 to 6 degrees of freedom. This improvement makes the motion and vestibular (the perception of body position and movement) much more realistic for drivers. In addition, the driving simulator has a 120-hertz (Hz) eye-tracking capability (that is, it takes 120 samples per second) so the researchers can investigate where participants are looking when they drive through the various roadway scenarios.
When FHWA introduced the double crossover diamond interchange design in the United States in 2004 in Springfield, MO, the driving simulator played an important role in testing human factors issues related to that interchange. Although France has used the double crossover diamond successfully for 30 years, this freeway interchange design was new to the United States. To assist with U.S. development, Michel Labrousse, director of the Centre d'Etudes Techniques de l'Equipment Normandie-Centre, provided records, signal layouts, and traffic flow and crash data from a groundbreaking installation in Versailles, France.
Many conventional interchanges in urban areas are congested and experience high crash rates. In comparison to a conventional diamond interchange, a double crossover diamond design involves drivers crossing over from the right side of the road to the left side and then back, thus combining left-turning and through traffic movements. Because of this novel design, one human factors concern was that drivers might become confused and make a dangerous maneuver. To evaluate this concern, the FHWA researchers created visualizations in the simulator of various driving scenarios.
This image from FHWA's driving simulator shows a sample scenario used in a human factors study of the double crossover diamond interchange
The Missouri Department of Transportation (MoDOT) designed and built the first U.S. double crossover diamond interchange in Springfield, MO, and opened it to traffic in June 2009. During the design phase, the Missouri engineers visited the Human Factors Laboratory to virtually drive through a simulated double crossover diamond. At the same time, the laboratory’s researchers provided feedback on the details of the MoDOT design. This visualization and testing in the driving simulator helped to alleviate safety concerns about the new design. The FHWA researchers then created video clips from the simulation scenarios to facilitate outreach to the Missouri public.
Researchers at FHWA's Human Factors Laboratory use this field research vehicle to conduct onroad experiments to understand driver behavior and performance better
A current study using the simulator examines issues related to driver distraction. Researchers are investigating whether advertising on changeable message signs is distracting to drivers. Some of the measures used in the study include the number and duration of eye glances to each sign, and whether participants notice a sign telling them to exit the freeway because there is a crash ahead. The researchers would also like to determine whether there is any correlation between potential distraction from advertising on changeable message signs and safety concerns. The study is in the data collection phase, and the results are expected to take another year.
A field research vehicle, an instrumented 2007 sport utility vehicle (SUV), is another tool in use at the Human Factors Laboratory. The SUV is outfitted with equipment to record GPS position, vehicle speed, and vehicle acceleration. The vehicle also is equipped with a state-of-the-art eye-tracking system that consists of two infrared light sources and three cameras mounted on the dashboard facing the driver. These cameras and lights are small and are not attached to the driver in any manner. The cameras are synchronized to the light sources and help track the head position and gaze of the driver.
An eye-tracking device (the three circled cameras) in this field research vehicle helps researchers study where drivers are looking when they drive through various roadway environments.
There are three additional cameras mounted on the exterior of the vehicle's roof, directly above the driver's position, for capturing the forward driving scene. The cameras capture the panorama of the driving scene in front of the vehicle, together providing an 80-degree-wide by 40-degree-high field of the forward view. The forward view area reaches from the left side of the windshield to a portion of the right side.
The research vehicle was used to collect data for a study to examine where drivers look when they are driving past commercial electronic variable message signs and standard billboards. The laboratory measured the signs and billboards with respect to luminance, location, size, and other relevant variables.
Another facility at the Human Factors Laboratory is known as the “sign lab,” but is formally called the Sign Design and Research Facility. This facility consists of a 60-inch (152-centimeter) light-emitting diode/liquid crystal display (LED/LCD) high-definition television connected to a computer control center. The sign lab enables researchers to present traffic signs to participants in a controlled environment. When developing new traffic signs, researchers need to determine the maximum distance at which participants can recognize and comprehend signs.
To do this, a participant sits at the computer and looks at the TV as a researcher displays a sign as a small distant object and then enlarges it so that its appearance approximates the way it would be viewed as a vehicle approaches the sign at a specified speed. The researcher then uses the size of the image at the moment the participant recognizes it to approximate the sign's recognition sight distance. The computer precisely controls the sign display duration and image size, and measures the participant's reaction time. The researcher generally records sign comprehension using open-ended questions relating to the participant's understanding of the traffic sign. For example, the research might ask, "If you were driving and saw this sign, what action would you take?"
When developing new traffic signs, researchers need to determine the maximum distance at which motorists can recognize and comprehend a sign. The FHWA sign lab, shown here, enables researchers to present traffic signs to participants in a controlled environment and study their responses.
Recently, FHWA researchers at the sign lab conducted two studies funded by the Traffic Control Device Consortium Pooled Fund Program, which combines States' funds into a pool for Federal research. The first study evaluated identification signs at freeway interchange approaches and the efficacy of the signs at providing motorists with information based on business logos. Currently, the Manual on Uniform Traffic Control Devices (MUTCD) limits the number of business logos on a single interchange approach sign to six. Whether increasing or decreasing this number would produce favorable results was one aspect of the study. The research also evaluated the effectiveness of using businesses' logos versus standard highway sign text.
The researchers showed 103 participants multiple combinations of four-, six-, and nine-panel signs. They displayed the signs on the television screen at a simulated distance of 121 feet (37 meters), approximately half the minimum legibility distance. Results suggested that participants were less able to identify specific business logos accurately compared to standard text on highway signs. (See www.pooledfund.org/Details/Study/281for more information)
Participants also needed more time to identify artistic logos. Across each of the panels, identification accuracy was higher starting at the top of the sign and shifting downward from left to right. In addition, more signs on a panel resulted in more eye glances away from the simulated road. Results from this study showed that any benefit of providing drivers with more service information, such as nine-panel signs, is outweighed by the potential risk of increasing driver distraction. The second study performed in the sign lab examined the legibility of multiple alternatives of symbols listed in the MUTCD. The alternatives were either currently used internationally, were State specific, or were generated by the lab or elsewhere. Each research participant evaluated each symbol. The team exposed the participants to scenarios containing each of the sign alternatives for each of the sign groups.
For legibility testing, the researchers used software designed to increase the size of the sign gradually, simulating how the sign would appear as a motorist drives toward it at a specified speed. The researchers then measured the legibility distance for each sign. Following each scenario, the team recorded the participants' comprehension using open-ended and multiple choice questions, and by the participants' rankings of how well they thought the signs would work.
Results showed that some alternatives clearly performed better than others, while other comparisons were not as definitive. For instance, under the multiple choice questions, alternative 2 of the WEAVE symbol clearly outperformed the three other alternatives, garnering correct responses 95 percent of the time. In the case of the four alternatives for the TRUCK ROLLOVER sign, however, the results revealed no statistically significant differences in performance.
In a study that examined sign legibility and drivers' comprehension, researchers asked participants to compare signs listed in the MUTCD to multiple alternatives.
In partnership with the National Highway Traffic Safety Administration (NHTSA), the Human Factors Laboratory also house a MiniSim™ driving simulator, a part-task simulator consisting of a quarter-cab setup that includes an adjustable driver's seat, driver controls such as pedals and a steering wheel, and a meter cluster including a speedometer. The MiniSim™ has three 42-inch (107-centimeter) forward-display LCD televisions, software, and computers for generating driving scenes and controlling vehicle dynamics.
The MiniSim™ shown here enables researchers to conduct low-cost studies to answer specific questions or preliminary research prior to a larger scale test.
The MiniSim™ is useful for evaluating driver performance in simple environments, such as various infrastructure-related studies that do not require the full immersion of high-fidelity driving simulation. This tool enables researchers to conduct low-cost studies to answer specific questions or to conduct preliminary research prior to a large-scale simulation or onroad research.
A recent study using the MiniSim™ examined driver performance on horizontal curves of rural two-lane roadways. According to the Fatality Analysis Reporting System, a total of 23,740 fatalities resulted from run-off-road crashes on the horizontal curve sections of rural two-lane roadways from 2005 to 2009 – an average of 4,748 fatalities per year. An analysis of the National Motor Vehicle Crash Causation Survey suggests that a driver who is familiar with a roadway is twice as likely to be involved in a run-off-road crash as one who is unfamiliar with it. In addition, a driver who is in a hurry is 3.2 times more likely to be involved in a run-off-road crash than one not in a hurry, and an inattentive driver is 3.7 times more likely to be in a crash than an attentive driver.
The research team examined possible procedures for establishing drivers' familiarity with a roadway, eliciting states of distraction because of being in a hurry, and determining the effect of these factors on driver performance on rural two-lane horizontal curves, as compared to baseline conditions. Measurements included vehicle speed and lane positioning.
Results indicate that the methodological procedures were effective at simulating the precipitating events and might be useful in future experiments by providing realistic driving situations for the development of dynamic traffic control devices using simulation.
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