Street-crossing Decisions Research Articles

Pedestrians' street-crossing decisions compared between conventional and electric vehicles

To safely cross a road before an approaching vehicle, pedestrians need to accurately judge the vehicle's motion. Recent studies from our lab demonstrated that the noise emitted by a vehicle conveys important information about its motion, particularly in the case of accelerating approaches. Here, we compared street-crossing decisions between conventional (ICEVs) and electric vehicles (EVs) with or without AVAS sounds. The experiment presented high-fidelity audiovisual VR simulations of approaching vehicles, based on recordings of real ICEVs and EVs. The presented velocity profiles included a large variation in acceleration rates, a = 0 to 4.4 m/s^2, and two velocities at the moment of the crossing decision (28 km/h versus 50 km/h). To investigate whether the lower sound level of EVs compared to ICEVs contributes to differences in crossing decisions, we additionally presented a condition in which the sound levels were matched between vehicle types. All experimental conditions were presented in two modality conditions (auditory-only and audiovisual). We compare the crossing decisions between vehicle types, velocity profiles and level profiles in terms of collision probabilities estimated from the measured psychometric functions. Preliminary results confirm differences between crossing decisions made in interaction with EVs compared to ICEVs, reduced in the level-matched conditions.

Do Simulated Augmented Reality Overlays Influence Street-Crossing Decisions for Non-Mobility-Impaired Older and Younger Adult Pedestrians?

This study used a virtual environment to examine how older and younger pedestrians responded to simulated augmented reality (AR) overlays that indicated the crossability of gaps in a continuous stream of traffic. Older adults represent a vulnerable group of pedestrians. AR has the potential to make the task of street-crossing safer and easier for older adults. We used an immersive virtual environment to conduct a study with age group and condition as between-subjects factors. In the control condition, older and younger participants crossed a continuous stream of traffic without simulated AR overlays. In the AR condition, older and younger participants crossed with simulated AR overlays signaling whether gaps between vehicles were safe or unsafe to cross. Participants were subsequently interviewed about their experience. We found that participants were more selective in their crossing decisions and took safer gaps in the AR condition as compared to the control condition. Older adult participants also reported reduced mental and physical demand in the AR condition compared to the control condition. AR overlays that display the crossability of gaps between vehicles have the potential to make street-crossing safer and easier for older adults. Additional research is needed in more complex real-world scenarios to further examine how AR overlays impact pedestrian behavior. With rapid advances in autonomous vehicle and vehicle-to-pedestrian communication technologies, it is critical to study how pedestrians can be better supported. Our research provides key insights for ways to improve pedestrian safety applications using emerging technologies like AR.

Ghost on the Windshield: Employing a Virtual Human Character to Communicate Pedestrian Acknowledgement and Vehicle Intention

Pedestrians base their street-crossing decisions on vehicle-centric as well as driver-centric cues. In the future, however, drivers of autonomous vehicles will be preoccupied with non-driving related activities and will thus be unable to provide pedestrians with relevant communicative cues. External human–machine interfaces (eHMIs) hold promise for filling the expected communication gap by providing information about a vehicle’s situational awareness and intention. In this paper, we present an eHMI concept that employs a virtual human character (VHC) to communicate pedestrian acknowledgement and vehicle intention (non-yielding; cruising; yielding). Pedestrian acknowledgement is communicated via gaze direction while vehicle intention is communicated via facial expression. The effectiveness of the proposed anthropomorphic eHMI concept was evaluated in the context of a monitor-based laboratory experiment where the participants performed a crossing intention task (self-paced, two-alternative forced choice) and their accuracy in making appropriate street-crossing decisions was measured. In each trial, they were first presented with a 3D animated sequence of a VHC (male; female) that either looked directly at them or clearly to their right while producing either an emotional (smile; angry expression; surprised expression), a conversational (nod; head shake), or a neutral (neutral expression; cheek puff) facial expression. Then, the participants were asked to imagine they were pedestrians intending to cross a one-way street at a random uncontrolled location when they saw an autonomous vehicle equipped with the eHMI approaching from the right and indicate via mouse click whether they would cross the street in front of the oncoming vehicle or not. An implementation of the proposed concept where non-yielding intention is communicated via the VHC producing either an angry expression, a surprised expression, or a head shake; cruising intention is communicated via the VHC puffing its cheeks; and yielding intention is communicated via the VHC nodding, was shown to be highly effective in ensuring the safety of a single pedestrian or even two co-located pedestrians without compromising traffic flow in either case. The implications for the development of intuitive, culture-transcending eHMIs that can support multiple pedestrians in parallel are discussed.

The Effect of Simulated Central Field Loss on Street-crossing Decision-Making in Young Adult Pedestrians.

This study explored the street-crossing decision-making performance of young normally sighted subjects with simulated central field loss (CFL). The results suggest that using eccentric viewing enables a person to make safe and reliable street-crossing decisions. This study tested the hypothesis that, as the diameter of an experimentally induced central scotoma increases, the accuracy and reliability of street-crossing decisions worsen. Street-crossing decisions were measured in 20 young subjects aged between 23 and 31 years while monocularly viewing a nonsignalized, one-way street for different vehicular arrival times. Using a 5-point rating scale, subjects judged whether they could cross the street before vehicular arrival with habitual vision and simulated CFL with eccentric viewing. The CFL was induced using soft contact lenses with different central opaque diameters. Using receiver operating characteristic curve analysis, we obtained subjects' accuracy (amount of time in seconds where subjects either overestimated or underestimated vehicular arrival time relative to their actual crossing time) and reliability (how quickly subjects transitioned from judging insufficient to sufficient time to cross relative to their actual crossing time). The centrally opaque contact lenses induced central scotomata with a mean (standard deviation) diameter of 17.12° (5.83°). No significant difference in street-crossing accuracy (P = .35) or reliability (P = .09) was found between the normal, habitual vision and simulated CFL conditions. No statistically significant correlations were found between scotoma diameter and the accuracy and reliability of subjects' street-crossing decisions (P = .83 and P = .95, respectively). The findings of this study suggest that adopting eccentric viewing enables a person to successfully mitigate the negative effects of an absolute central scotoma on the accuracy and reliability of their street-crossing decisions.

Risk-taking, emotions and socio-cognitive dynamics of pedestrian street-crossing decision-making in the city

This study investigates pedestrian street-crossing decision-making to better appreciate both the complexity and the dynamics of this activity by analyzing the cognitive, emotional and social processes involved in such situations. We consider street-crossing decision-making in the context of situational awareness (Endsley’s model) by exploring other variables that may influence the decision-making: time pressure, emotions and social influence. Twenty participants were included in the study. They were instructed to negotiate two 1 km-routes in a large city using a paper map. After each route, they were invited to participate in an elicitation interview. A time pressure context was added for half of the participants. The originality of the method was based on the mixed approach of observable variables (video recordings from the viewpoint of the pedestrian and of an external observer) and the subjective experience of the street crossing by the pedestrian (e.g., perception, thoughts, feelings, anticipation) according to the situation’s dynamics. In total, the data included 67 elicited and recorded street crossings. The data indicated that approximately one-third of the street-crossing decisions were risky. In our observations, street-crossing decision-making was modulated by street-crossing habits, the environment configuration, the social influence, the learning of the road situation and the vehicle behavior. This study accounts for the complexity of street-crossing, the related risk and its links with feelings.

A vibrotactile wristband to help older pedestrians make safer street-crossing decisions

IntroductionOlder pedestrians are overrepresented in fatal accidents. Studies consistently show gap-acceptance difficulties, especially in complex traffic situations such as two-way streets and when vehicles approached rapidly. In this context, the present research was aimed at assessing the effectiveness of a vibrotactile device and study older pedestrian’s behavior when wearing the wristband designed to help them make safer street-crossing decisions. MethodTwenty younger-old participants (age 60–69), 20 older-old participants (age 70–80) and 17 younger adults (age 20–45) carried out a street-crossing task in a simulated two-way traffic environment with and without a vibrotactile wristband delivering warning messages. ResultsThe percentage of decisions that led to collisions with approaching cars decreased significantly when participants wore the wristband. Benefits tended to be greater particularly among very old women, with fewer collisions in the far lane and when vehicles approached rapidly when they wore the wristband. But collisions did not fall to zero, and responses that were in accordance with the wristband advice went up to only 51.6% on average, for all participants. The wristband was nevertheless considered useful and easy to use by all participants. Moreover, behavioral intentions to buy and use such a device in the future were greater in both groups of older participants, but not among the younger adults. Practical applicationsThis haptic device was able to partly compensate for some age-related gap-acceptance difficulties and reduce street-crossing risks for all users. These findings could be fruitfully applied to the design of devices allowing communication between vehicles, infrastructures, and pedestrians.

Training the elderly in pedestrian safety: Transfer effect between two virtual reality simulation devices

ObjectivesA virtual-reality training program has been developed to help older pedestrians make safer street-crossing decisions in two-way traffic situations. The aim was to develop a small-scale affordable and transportable simulation device that allowed transferring effects to a full-scale device involving actual walking. Methods20 younger adults and 40 older participants first participated in a pre-test phase to assess their street crossings using both full-scale and small-scale simulation devices. Then, a trained older group (20 participants) completed two 1.5-h training sessions with the small-scale device, whereas an older control group received no training (19 participants). Thereafter, the 39 older trained and untrained participants took part in a 1.5-h post-test phase again with both devices. ResultsPre-test phase results suggested significant differences between both devices in the group of older participants only. Unlike younger participants, older participants accepted more often to cross and had more collisions on the small-scale simulation device than on the full-scale one. Post-test phase results showed that training older participants on the small-scale device allowed a significant global decrease in the percentage of accepted crossings and collisions on both simulation devices. But specific improvements regarding the way participants took into account the speed of approaching cars and vehicles in the far lane were notable only on the full-scale simulation device. DiscussionThe findings suggest that the small-scale simulation device triggers a greater number of unsafe decisions compared to a full-scale one that allows actual crossings. But findings reveal that such a small-scale simulation device could be a good means to improve the safety of street-crossing decisions and behaviors among older pedestrians, suggesting a transfer of learning effect between the two simulation devices, from training people with a miniature device to measuring their specific progress with a full-scale one.

Is Mild Dementia Related to Unsafe Street-Crossing Decisions?

The overrepresentation of very old people (75 or older) in pedestrian crash statistics raises the issue of the effects of normal and pathologic ageing on gap-selection difficulties during street crossing. The present study focused on Alzheimer disease, a condition commonly associated with cognitive declines detrimental to daily life activities such as crossing the street. Twenty-five participants with mild dementia and 33 controls carried out a street-crossing task in a simulated environment. They also took a battery of cognitive tests. The mild-dementia group was more likely than the control group to make decisions that led to collisions with approaching cars, especially when the traffic was coming from 2 directions and they were in the far lane. Regression analyses demonstrated that the increased likelihood of collisions in the dementia group was associated with impairments in processing-speed and visual-attention abilities assessed on the Useful Field of View test. This test has already proven useful for predicting driving outcomes, falls, and street-crossing difficulties in healthy old adults, and among drivers with Alzheimer disease. Clinicians are encouraged to use it to help estimate whether a patient can drive, walk, and cross a street safely.

Influence of Ambient Sound Fluctuations on the Crossing Decisions of Pedestrians who Are Visually Impaired: Implications for Setting a Minimum Sound Level for Quiet Vehicles

Introduction Following the passage of the Pedestrian Safety Enhancement Act in the United States, the National Highway Traffic Safety Administration is setting a minimum sound level for hybrid and battery electric vehicles. With an aim to aid this effort, the present study investigated the timing and performance of critical street-crossing decisions by pedestrians who are visually impaired (that is, those who are blind or have low vision) at selected intersections. Methods Fourteen visually impaired adults with typical hearing along with a sighted experimenter made street-crossing decisions by indicating when they would initiate crossing using radio controller handsets. Participants’ decisions were compared with the sighted experimenter's decisions to determine the level of their risk. Results At the residential intersection, the percentage of risky crossing decisions by participants was significantly lower when the decisions were made at lower ambient sound levels (M = 8.9%, SD = 6.9%) than when they were made at higher ambient sound levels (M = 35.3%, SD = 21.2%), p < .001. The participants were able to make significantly fewer risky crossing decisions during the windows of time when the ambient sound level was lower at the major-and-minor-street intersection as well ( p = .001). Discussion Participants were often able to take advantage of the troughs in ambient sound for making street-crossing decisions, and the decisions made in lower ambient sound level conditions were generally less risky than those made in higher ambient sound level conditions. Implications for practitioners Given the finding that the level of ambient sound detected when participants made crossing decisions was much lower than the average ambient sound level at a given intersection, as long as there are noticeable dips in ambient sound, average ambient sound level at a given intersection may not be the most relevant measure of background sound level when determining a minimum sound level for the hybrid and electric vehicles.

Adapting a Driving Simulator to Study Pedestrians’ Street-Crossing Decisions: A Feasibility Study

The decision when to cross a street safely is a challenging task that poses high demands on perception and cognition. Both can be affected by normal aging, neurodegenerative disorder, and brain injury, and there is an increasing interest in studying street-crossing decisions. In this article, we describe how driving simulators can be modified to study pedestrians’ street-crossing decisions. The driving simulator’s projection system and the virtual driving environment were used to present street-crossing scenarios to the participants. New sensors were added to measure when the test person starts to cross the street. Outcome measures were feasibility, usability, task performance, and visual exploration behavior, and were measured in 15 younger persons, 15 older persons, and 5 post-stroke patients. The experiments showed that the test is feasible and usable, and the selected difficulty level was appropriate. Significant differences in the number of crashes between young participants and patients (p = .001) as well as between healthy older participants and patients (p = .003) were found. When the approaching vehicle’s speed is high, significant differences between younger and older participants were found as well (p = .038). Overall, the new test setup was well accepted, and we demonstrated that driving simulators can be used to study pedestrians’ street-crossing decisions.

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.

Functional declines as predictors of risky street-crossing decisions in older pedestrians

The experiment investigated the extent to which risky street-crossing decisions by older pedestrians can be explained by declines in functional abilities. Sixteen young (age 20–35), 17 younger-old (age 60–67), and 18 older-old (age 70–84) participants carried out a street-crossing task in a simulated two-way road environment and took a battery of tests assessing perceptual, cognitive, and motor abilities. Older-old pedestrians were more likely than young and younger-old participants to make decisions that would have led to collisions with approaching cars, especially when traffic coming from two directions was approaching at a high speed. Regression analyses identified several functional performance measures as predictors of these dangerous choices. Walking speed, which determined the time needed to cross, was shown to play the most important role. Time-to-arrival estimate, which informed the pedestrians about the time available for crossing, was found to be the second most predictive factor. Visual processing speed and visual attention abilities assessed via the UFOV® Test also came into play, allowing participants to focus their attention on the relevant available information and to make timely, correct decisions. Attention shifting was the fourth significant predictor, allowing pedestrians to adapt their crossing strategy to the oncoming road-traffic information. The results suggest that the greater risk of being involved in a collision as age increases calls for a multi-dimensional explanation combining age-related physical, perceptual, and cognitive performance declines. These findings have implications for improving older pedestrians’ safety in terms of speed limits, road design, and training.

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 population's 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.

Street-Crossing Decision-Making: A Comparison between Patients with Age-Related Macular Degeneration and Normal Vision

We determined whether the street-crossing decisions of subjects with age-related macular degeneration (AMD) were as accurate and precise as those made by young and older subjects with normal vision. Street-crossing decisions in 13 AMD subjects, and 20 young and 20 older control subjects with normal vision were measured along an un-signalized street for nine different gap times. After calculating the discriminability (d') of the street-crossing decision variable for all gap pairs and entering these d' values into a one-dimensional scaling model, the means of each distribution of the decision variable relative to a "center of gravity" were estimated and plotted against gap time. The resultant plot was a nonlinear function. Street-crossing decision accuracy was computed for each subject as the difference between the x-intercept of the nonlinear function (t(COG)) and subjects' measured street-crossing time. Street-crossing decision-making precision was computed as the value of the slope of the nonlinear function at t(COG). We found that all subjects were precise in their street-crossing decisions (P = 0.55). Significant differences in street-crossing accuracy were found as a function of age (P = 0.003). Compared to either the older normally-sighted (P = 0.018) or AMD (P = 0.019) subjects, the young normally-sighted subjects made the least accurate street-crossing decisions. No significant difference in accuracy was found between the AMD and age-matched normally-sighted subjects (P = 0.90). Our data suggested that age and mild central vision loss did not affect significantly a subject's precision in their street-crossing decisions. Age, but not mild central vision loss, significantly affected a subject's accuracy in their street-crossing decisions.

Misjudging Their Own Steps

The aim of this study was to test whether elderly individuals underestimate the time that it will take them to cross a street by comparing estimated with actual road-crossing time. In many developed countries, elderly people are overrepresented among pedestrian fatalities from motor vehicle accidents. There is surely more than one contributing factor to this phenomenon, and many have been offered. We propose that one additional factor may be that although older people are consciously aware that they no longer walk at the same pace as they once did, they do not take this fact into consideration when planning a street crossing. We compared the ability of young and old pedestrians to estimate the time that it will take them to cross a street, using both prospective and retrospective time estimation. A significant interaction was found between age group and crossing time. Among elderly participants, actual crossing times were significantly longer than both their precrossing estimation and their postcrossing estimation, which did not significantly differ from each other. In contrast, the undergraduate group's crossing times did not display a significant difference across measurements. This study implies that even if older pedestrians correctly evaluate the road situation, they may nonetheless endanger themselves by underestimating the time that it will take them to cross the street.We suggest that minimizing this effect could be accomplished by educating seniors to the fact that they are not as fast as they once were and that this fact needs to be factored in to street-crossing decisions.

Measurements of street-crossing decision-making in pedestrians with low vision

PurposeCrossing the street is an important but risky activity of daily living. If a pedestrian makes a poor street-crossing decision, the consequence could be serious injury or death. In order to advance our understanding of how visual and auditory information is sampled and processed to make street-crossing decisions, an accurate, reliable, and sensitive psychophysical and/or psychometric method of measurement of the street-crossing decision variable must first be developed and validated. The aim of this paper is to develop and validate a new metric for this variable. MethodsUsing a 5 point rating scale, safety ratings for eight different vehicular gap times of different durations were recorded along an unsignalized, two-lane street of one-way traffic. Safety ratings were collected from 12 normally sighted and 10 visually impaired subjects. Receiver Operating Characteristic (ROC) curves were estimated for all possible gap pairs and the discriminability (d′) of the street-crossing decision variable for all gap pairs was estimated from the area under the ROC curve. ResultsWe found that our data conform with the assumptions that the underlying distributions of the decision variable are continuous, monotonic and unbounded. Using the dissimilarity matrix of d’ values for each person (which were computed for all pairings of gap times) in a one-dimensional scaling model, we estimated the means of each distribution of the decision variable relative to a center of gravity (COG) for the person. When plotting the means of the distributions against vehicular gap time, the data are best described as a non-linear function symmetric about the COG. We showed that the x-intercept (tCOG) and slope from the non-linear function can be used to assess a person's street-crossing decision-making performance for different amounts of sensory information. Using our newly developed metrics, we found no significant difference in tCOG (p=0.30) and in the slopes of the model (p=0.85) between normally sighted and visually impaired subjects. In addition, both subject groups centered their tCOG close to their actual crossing time. ConclusionsA newly developed model for measuring a street-crossing decision variable functions as a valid metric that can be used to quantify street-crossing decision-making performance in pedestrians. Using this new metric, we observed that visually impaired subjects who travel independently are able to make street-crossing judgments that are comparable to those of normally sighted subjects.

Can simulator-based training improve street-crossing safety for elderly pedestrians?

Older adults are known to be over-involved in pedestrian fatalities. Past research has shown that many of them make unsafe decisions when vehicles are approaching at a high speed and also miss many crossing opportunities when vehicle speed is low. They seem to have trouble taking the speed of approaching cars into account and predominantly base their crossing decisions on vehicle distance. A randomized controlled design was employed here to evaluate the effectiveness of combined behavioural and educational interventions on crossing decisions. Forty seniors aged 60 years and older were randomly assigned to an intervention group receiving a simulator-based street-crossing training programme (n = 20), or a control group (unrelated internet-use training course, n = 20). Baseline data and post-intervention data (immediately after, and 6 months after training) were collected, and included street-crossing decisions and behaviours on a simulated street-crossing task. Although the groups did not differ significantly from each other on the baseline measures, the results showed significant group differences immediately after training: intervention-group participants crossed more rapidly, adopted larger safety margins, and had fewer tight fits than participants in the control group. However, 6 months after training, significant group differences were no longer observed: improvements in street crossing decisions and behaviours were apparent for both intervention and control groups. These results indicate a clear shift of the decision criterion towards more safety for all participants over time. However, the ability to take the oncoming car’s speed into account did not improve: on both post-intervention tests, both groups of participants still made more unsafe decisions when the car was approaching at a high speed and missed more crossing opportunities at a low speed. This finding may reflect age-related perceptual and cognitive difficulties that cannot be remedied by a behavioural or educational training method. Implications for further research and opportunities for enhanced training interventions are discussed.

Crossing a Multi-Lane Street: Irrelevant Cars Increase Unsafe Behavior

Before crossing a road or an intersection, road users have to determine among the surrounding traffic whether or not they have enough time to safely complete their maneuver. 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. We conducted a simulator experiment in which observers indicated whether or not they had enough time to complete safe street crossing. Traffic gaps were presented either with a single or two oncoming cars on different lanes, in such a way that in all cases, only the shortest gap was taskrelevant. Nevertheless, street-crossing decisions were found to be also influenced by the task-irrelevant longer gap, observers being more willing to cross the street when having to judge two gaps simultaneously compared to only one gap. Consequences of this unsafe behavior are discussed.

Age-related differences in street-crossing safety before and after training of older pedestrians

International accident statistics indicate that elderly pedestrians make up an extremely vulnerable road-user group. Past research has shown that older adults make many unsafe street-crossing decisions and adopt insufficient safety margins, especially when vehicles are approaching at high speed. Apart from studies on road design and speed-limit countermeasures, there is surprisingly no road-safety research on behavior-based measures to improve older pedestrians’ safety. In this line, the present study was aimed at (i) assessing the effectiveness of a training program for older pedestrians that combined behavioral and educational interventions, and (ii) examining whether and to what extent age-related differences in street-crossing safety could be reduced after training older adults. Twenty seniors were enrolled in a training program. Before, immediately after, and six months after training, street-crossing behavior was assessed using a simulated street-crossing task. Twenty younger participants performed the same simulated task to obtain a baseline measure. The results showed that the training produced significant short- and long-term benefits, due to a shifting of the decision criteria among the older participants towards more conservative judgments. When compared with the younger group, the older participants improved their behavior considerably so that significant differences in the mean safety-related indicators were no longer observed. However, the older participants’ ability to take the oncoming car's speed into account did not improve. Even after training, and contrary to younger adults, older participants were found to make more and more unsafe decisions as the car's speed increased, putting them at a higher risk at high speeds. This finding may reflect age-related perceptual and cognitive difficulties that cannot be remedied by a behavioral or educational training method. The present findings underline that high speed is an important risk factor for elderly pedestrians that should be handled by effective speed reduction measures (i.e. speed ramps, road narrowing).

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.