Viola Cavallo

The effects of aging on street-crossing behavior: from estimation to actual crossing

Based on an interactive road-crossing task, this study examined age-related effects on crossing decisions and whether or not age affects behavioral adjustments to the time gap. It also compared crossing-task decisions to previously observed estimation-task decisions [Lobjois, R., Cavallo, V., 2007. Age-related differences in street-crossing decisions: the effects of vehicle speed and time constraints on gap selection in an estimation task. Accident Analysis and Prevention 39 (5), 934-943]. The results showed that older adults selected a greater mean time gap and initiated their crossing sooner than the younger ones, indicating an attempt to compensate for their increased crossing time. However, older adults accepted shorter and shorter time gaps as speed increased, putting them at a higher risk at high speeds. Regarding adaptive behavior, the analyses showed that all groups adjusted their crossing time to the available time. Comparison of crossing decisions and estimations revealed that the young group had a greater number of tight fits and missed fewer opportunities on the crossing task, whereas these differences did not appear in the elderly. This suggests that the crossing decisions of younger adults are much more finely tuned to time gaps in actual crossing tasks than in estimation tasks and that older adults have trouble calibrating perception and action and perceiving possibilities for action.

The role of perceptual, cognitive, and motor abilities in street-crossing decisions of young and older pedestrians

Citation information: Dommes A & Cavallo V. The role of perceptual, cognitive, and motor abilities in street‐crossing decisions of young and older pedestrians. Ophthalmic Physiol Opt 2011, 31, 292–301 doi: 10.1111/j.1475‐1313.2011.00835.x

The effects of age and traffic density on street-crossing behavior

Past research has shown that road users accept shorter time gaps when the waiting time/number of vehicles they let pass before attempting to merge into the traffic increases. While elderly pedestrians are known to be an extremely vulnerable group of road users, very few studies dealt with the effect of environmental constraints and crossing complexity on this populations safety. The present study aimed at determining whether or not street-crossing decisions and behavior of younger and older pedestrians were differently affected by a traffic flow. In an interactive street-crossing task, we assessed whether mean time gap and crossing decisions depended on the position of the gap pedestrians selected into the traffic stream. Results revealed that irrespective of their age pedestrians accepted a smaller time gap when they chose the second interval of the traffic compared to the first one. Contrasting with previous hypotheses, this traffic-related behavior was not accompanied by an increase in the decisions risk. The findings also showed that the transition threshold from rejecting to accepting time gaps was shorter when the second interval was selected compared to the first one. This increment in task constraints might help younger and older pedestrians alike to perceive action possibilities more accurately and to be better attuned to traffic conditions by comparing gaps between each other. This opens an interesting perspective in the understanding and the training of the ability of elderly road users to remain accurate in their judgements.

Crossing a two-way street: comparison of young and old pedestrians

INTRODUCTION Choosing a safe gap in which to cross a two-way street is a complex task and only few experiments have investigated age-specific difficulties. METHOD A total of 18 young (age 19-35), 28 younger-old (age 62-71) and 38 older-old (age 72-85 years) adults participated in a simulated street-crossing experiment in which vehicle approach speed and available time gaps were varied. The safe and controlled simulated environment allowed participants to perform a real walk across an experimental two-way street. The differences between the results for the two lanes are of particular interest to the study of visual exploration and crossing behaviors. RESULTS The results showed that old participants crossed more slowly, adopted smaller safety margins, and made more decisions that led to collisions than did young participants. These difficulties were found particularly when vehicles approached in the far lane, or rapidly. Whereas young participants considered the time gaps available in both lanes to decide whether to cross the street, old participants made their decisions mainly on the basis of the gap available in the near lane while neglecting the far lane. CONCLUSIONS The present results point to attentional deficits as well as physical limitations in older pedestrians. Several practical and have implications in terms of road design and pedestrian training are proposed.

Are car daytime running lights detrimental to motorcycle conspicuity

For a long time, motorcycles were the only vehicles with daytime running lights (DRLs), but this conspicuity advantage has been questioned due to the rapidly increasing introduction of DRLs on cars as well. The present experiment was designed to assess effects of car DRLs on motorcycle perception in a situation that specifically brought attentional conspicuity to bear. Photographs representing complex urban traffic scenes were displayed briefly (250 ms) to 24 participants who had to detect vulnerable road users (motorcyclists, cyclists, pedestrians) appearing at different locations and distances. Car DRLs hampered motorcycle perception compared to conditions where car lights were not on, especially when the motorcycle was at a greater distance from the observer and when it was located in the central part of the visual scene. Car DRLs also hampered the perception of cyclists and pedestrians. Although the globally positive safety effect of car DRLs is generally acknowledged, our study suggests that more attention should be paid to motorcyclists and other vulnerable road users when introducing car DRLs. Several means of improving motorcycle conspicuity in car DRL environments are discussed.

Arrival-time judgments on multiple-lane streets: The failure to ignore irrelevant traffic

How do road users decide whether or not they have enough time to cross a multiple-lane street with multiple approaching vehicles? Temporal judgments have been investigated for single cars approaching an intersection; however, close to nothing is known about how street crossing decisions are being made when several vehicles are simultaneously approaching in two adjacent lanes. This task is relatively common in urban environments. We report two simulator experiments in which drivers had to judge whether it would be safe to initiate street crossing in such cases. Matching traffic gaps (i.e., the temporal separation between two consecutive vehicles) were presented either with cars approaching on a single lane or with cars approaching on two adjacent lanes, either from the same side (Experiment 1) or from the opposite sides (Experiment 2). The stimuli were designed such that only the shortest gap was decision-relevant. The results showed that when the two gaps were in sight simultaneously (Experiment 1), street-crossing decisions were also influenced by the decision-irrelevant longer gap. Observers were more willing to cross the street when they had access to information about the irrelevant gap. However, when the two gaps could not be seen simultaneously but only sequentially (Experiment 2), only the shorter and relevant gap influenced the street-crossing decisions. The results are discussed within the framework of perceptual averaging processes, and practical implications for road safety are presented.

Improving motorcycle conspicuity through innovative headlight configurations

Most motorcycle crashes involve another vehicle that violated the motorcycles right-of-way at an intersection. Two kinds of perceptual failures of other road users are often the cause of such accidents: motorcycle-detection failures and motion-perception errors. The aim of this study is to investigate the effect of different headlight configurations on motorcycle detectability when the motorcycle is in visual competition with cars. Three innovative headlight configurations were tested: (1) standard yellow (central yellow headlight), (2) vertical white (one white light on the motorcyclists helmet and two white lights on the fork in addition to the central white headlight), and (3) vertical yellow (same configuration as (2) with yellow lights instead of white). These three headlight configurations were evaluated in comparison to the standard configuration (central white headlight) in three environments containing visual distractors formed by car lights: (1) daytime running lights (DRLs), (2) low beams, or (3) DRLs and low beams. Video clips of computer-generated traffic situations were displayed briefly (250ms) to 57 drivers. The results revealed a beneficial effect of standard yellow configuration and the vertical yellow configuration on motorcycle detectability. However, this effect was modulated by the car-DRL environment. Findings and practical recommendations are discussed with regard to possible applications for motorcycles.