Dr. Jodie Plumert

Bicycling across Traffic-Filled Roads

Bicycling injuries represent a significant public health problem in the United States. Approximately 600,000 bicycle-related injuries are treated in emergency rooms each year. Five- to 15-year-old children represent a particularly vulnerable segment of the population, having the highest rate of injury per million cycling trips. Motor vehicles are involved in approximately one-third of all bicycle-related brain injuries and in 90% of all fatalities resulting from bicycle crashes. A critical first step in developing programs to prevent collisions between bicycles and motor vehicles is understanding why such collisions occur. Our work focuses on how immature perceptual-motor functioning may put children at risk for car-bicycle collisions when crossing roads. The overarching aim of this research is to bring together the study of basic and applied issues into a single program of research (Schwebel, Plumert, & Pick, 2000).

We have developed an immersive, interactive bicycling simulator to examine the gaps children and adults accept when bicycling across traffic-filled intersections in a virtual environment (go to Hank Virtual Environments Lab). Participants ride an actual bicycle mounted on a stationary frame that is positioned in the middle of three 10 ft wide x 8 ft high screens. High-resolution, textured graphics provide participants with 270 degrees of nonstereoscopic, immersive visual imagery. The bicycle is instrumented to sense steering angle, hand braking, and pedaling torque applied by the rider. Real-world dynamics are simulated through a torque motor that actively drives the bicycle�s rear wheel. The bicycle dynamics model accounts for rider and bicycle mass and inertia, terrain slope, ground friction, wind resistance, and so on.


Ten- and 12-year-olds and adults ride through a virtual environment consisting of a straight, residential street with multiple intersections. Their task is to cross the intersections without getting hit by a car. Participants face cross traffic from their left-hand side and wait for gaps they judge are adequate for crossing. The cross traffic travels at continuous rates of either 25 or 35 mph with randomly ordered temporal gaps between vehicles. This work shows that relative to adults, children�s gap choices and road-crossing behavior are less well matched. Children and adults choose the same size gaps and yet children end up with less time to spare when they cleared the path of the approaching car. A major reason why children end up with less time to spare than adults is that they delay initiation of movement. Our current work focuses on determining why children delay initiation of movement relative to adults and on peer influences on children's road-crossing decisions.

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Judging Distance in Real and Virtual Environments

Virtual environments have gained widespread use in recent years as a tool for studying human behavior. Problems ranging from how children make road-crossing decisions to how adults respond to social situations have been studied using various kinds of immersive virtual environments. Virtual environments have also been used as a tool for training new skills, particularly in cases where training in the real environment can be risky or dangerous. For example, virtual environments have been used for training fire fighters, medical doctors, and military personnel. Two questions that arise when using virtual environments for such research and training purposes are: 1) How well does perception in virtual environments correspond to perception in the real environment? and 2) How does experience in a virtual environment affect subsequent perception in the real environment and vice versa? Our work addresses both of these questions by investigating how people perceive distance in real and virtual environments both before and after experience in each environment.

Our work shows that people exhibit greater underestimation of distance in the virtual environment than in the real environment. However, this difference between the real and the virtual environment is wiped out by previous experience in the other environment. When people experience the virtual environment first they underestimate more than they normally would in the real environment. Likewise, when people experience the real environment first they underestimate less than they normally would in the virtual environment. This order effect is stronger when going from the real environment to the virtual environment than vice versa. One question these results raise is do these experiences actually affect visual perception? At this point, we believe the answer is no. Although we cannot completely rule out changes in visual perception, we propose that these effects result from the interaction of longer and shorter term memories of the larger environment and the target locations. During their initial experience with estimating distances in either the real or the virtual environment, people undoubtedly build up spatial representations of the entire environment and the target locations. We propose that these longer term spatial memory representations exert an influence when people make subsequent distance estimates in the other environment. Our current work focuses on how experience with differently scaled virtual environments affects subsequent distance perception.

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