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Unobtrusive observations of bicyclists were conducted at two-way, three-way, and four-way stop-controlled intersections. Consistent with previous reports, most cyclists did not stop at the stop sign. However, most cyclists did exhibit safety-related behaviors by making accommodations for traffic conditions. It was found that the cyclists conducted precautionary visual search when approaching stop signs, and that they were more likely to slow substantially or stop if cross traffic was not controlled by stop signs or if there were potential conflicts from other road users. Implications for safety interventions are discussed.

Because of differences between how a human and a camera (or digital recording system) acquire and process information, a representation (e.g., a photograph) of a scene may vary in how accurately it portrays what a human would perceive, particularly at low illumination levels. Ayres (1996) described a methodology by which a representation can be matched to observations made at the scene. Central to this process is the utilization of a reference chart to validate the representation. The efficacy of the original chart has been documented empirically; however, its utility can be restricted under certain lighting and viewing conditions. The current paper introduces and tests new reference charts designed to offer a wider range of applicability and with finer gradations of contrast. The new charts were found to be useful at illumination levels ranging from approximately 0.05 to 10.0 footcandles. Potential applications for the charts, including forensic purposes, are discussed.

It is not surprising that many multi-vehicle collisions occur at intersections, as intersecting streets present potential conflict situations where vehicle paths can cross one another. What does surprise both naïve observers and many professionals involved in accident investigations (e.g., accident reconstructionists, human factors scientists, lawyers) is the explanation that most red light running accidents happen only when the vehicle violating the red light enters the intersection approximately 4 to 6 seconds or more after the light has turned red. This paper provides a framework to study the conditions under which red light running collisions occur. This framework is applied to real-world intersection geometries and red light running collisions captured on video. A comparison of observational and crash data indicates that only a small fraction of red light running results in collisions. The mathematical framework can be used to develop likely timing scenarios in accident investigation, and can be expanded to study motor vehicle collisions with bicyclists or pedestrians.

When faced with a potential hazard, drivers often need to evaluate the situation and choose an avoidance maneuver quickly. Studies of emergency perception-response time by drivers have reported a range of mean values, and a number of factors have been identified or proposed to account for some of the variability between and within studies. One factor that has not attracted much attention in this literature is response accuracy. We propose that examination of this literature from within a speed/accuracy tradeoff framework may help explain some of the range of findings in driver reaction time research. This perspective may be useful when applying research results to practical questions such as motor vehicle accident reconstruction.

We examined several variables that can affect slip-resistance measurements obtained using the English XL tribometer to illustrate the importance of implementing the proper controls when using the device to evaluate a slip-and-fall incident. We measured slip resistance at two different locations on the same surface, under wet and dry conditions, with the tribometer oriented in eight different directions per location. Our results showed that location, direction, and surface wetness can affect slip resistance measurements, but the effects interact with each other in unpredictable ways. Discussion focuses on the importance of considering direction as well as location of a particular slip-and-fall, rather than strict adherence to ASTM F1679–04: Standard Test Method for Using a Variable Incidence Tribometer (VIT). We conclude that it is important to consider both location and direction when using the tribometer in analysis of any specific incident occurring on non-uniform surfaces.

It is well known that conversation (e.g., on a cell phone) impairs driving. We demonstrate that the reverse is also true: Language production and comprehension, and the encoding of the products of comprehension into memory, are less accurate when one is driving. Ninety-six pairs of drivers and conversation partners engaged in a story-retelling task in a driving simulator. Half of the pairs were older adults. Each pair completed one dual-task block (driving during the retelling task) and two single-task control blocks. The results showed a decline in the accuracy of the drivers' storytelling and of their memory for stories that were told to them by their nondriving partners. Speech production suffered an additional cost when the difficulty of driving increased. Measures of driving performance suggested that the drivers gave priority to the driving task when they were conversing. As a result, their linguistic performance suffered.

A total of 96 pairs of older and younger drivers participated in a study assessing the effects of conversation on the driving performance of older and younger drivers in a simulated city environment. These effects were investigated while drivers conversed with an in-vehicle passenger or an outside-vehicle caller. All of the passengers completed three separate, counterbalanced blocks of tasks that consisted of two single-task blocks (driving only and conversing only) and one dual-task block (driving and conversing). The results showed greater variability in velocity, lane keeping and steering control under single-task than under dual-task conditions. Drivers also showed greater average velocity and greater deviation from the center of the lane under single-task than under dual-task conditions. However, when crossing an intersection, a task requiring greater attentional resources, drivers exhibited a cost due to the dual task. The authors' data are consistent with the literature, which suggests that a secondary task may aid in the performance of a routinized task but may also impose costs if the primary task requires significant attentional resources. Older drivers exhibited greater variability in velocity, stayed closer to the center of the lane, and waited longer to cross intersections than their younger counterparts, suggesting that they compensate for their declining perceptual and cognitive abilities through changes in driving behavior. Drivers exhibited greater variability in steering under single-task conditions when talking to an outside-vehicle caller, and older drivers showed greater variability in velocity when conversing with an outside-vehicle caller.