Posts Tagged HFES

Visual search strategies of child-pedestrians in road crossing tasks

Hagai Tapiro, Anat Meir, Yisrael Parmet & Tal Oron-Gilad

Presentation at HFES-EU Annual meeting, Torino 2013


Children are over-represented in road accidents, often due to their limited ability to perform well in road crossing tasks. The present study examined children’s visual search strategies in hazardous road-crossing situations. A sample of 33 young participants (ages 7-13) and 21 adults observed 18 different road-crossing scenarios in a 180° dome shaped mixed reality simulator. Gaze data was collected while participants made the crossing decisions. It was used to characterize their visual scanning strategies. Results showed that age group, limited field of view, and the presence of moving vehicles affect the way pedestrians allocate their attention in the scene. Adults tend to spend relatively more time in further peripheral areas of interest than younger pedestrians do. It was also found that the oldest child age group (11-13) demonstrated more resemblance to the adults in their visual scanning strategy, which can indicate on a learning process that originates from gaining experience and maturation. Characterization of child pedestrian eye movements can be used to determine readiness for independence as pedestrians. The results of this study, emphasize the differences among age groups in terms of visual scanning. This information can contribute to promote awareness and training directions.

Dirichlet regression model and analysis

For each scenario, five areas of interest were defined (as shown in the Figure). The close range central area was defined as the 10 meters of road in each side from the pedestrian’s point of view (AOI 3). Then symmetrically areas to the right of the center and to the left were defined. The medium right/left range (AOIs 2/4) was the part of the road distant at least 10 meter to the right/left of the point of view but less than 100 meters away. The far right/left range (AOIs 1/5) was the part of the road at least 100 meter or more to the right/left of the pedestrian point of view.



Open this link to see a sample video of a scenario as seen by a young pedestrian

Why Dirichlet?

  • For each participant and scenario, the total Gaze distribution over the five AOI’s sums up to one.
  • Therefore Gaze distribution is compositional data i.e., non-negative proportions with unit-sum.
  • These types of data arise whenever we classify objects into disjoint categories and record their resulting relative frequencies, or partition a whole measurement into percentage contributions from its various parts.
  • Attempts to apply statistical methods for unconstrained data often lead to inappropriate inference.
  • Dirichlet regression suggested by Hijazi and Jernigan (2009) is more suitable for such cases.

How to use?

  • The Dirichlet regression model was fitted using DirichletReg package, in R Language. Applying a backward elimination procedure found the best fitting model has three significant main effects.

What did we find?

  • The dependent variable was the vector of AOIs and the independent variables were Age-group, POV and FOV; all of them were statistically significant (p <0.05). Predicted means for the percentage of time spent in each AOI for each age group based on the Dirichlet regression model are shown in the following figure and reveal differences among age groups. Note how children aged 9-10 spend more time gazing at the central area, note also the differences between mid-left and mid-right.
Predicted means (in each AOI) using Dirichlet model across all scenarios per age group

Predicted means (in each AOI) using Dirichlet model across all scenarios per age group

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“Coming soon to a conference near you” – presentations and posters for the summer and fall of 2012

This summer our team will be presenting at the ICTTP 2012.

Child pedestrian road crossing behavior

  • Studies in hazard perception in driving focus mainly  on paradigms where participants are asked to observe short video clips of traffic situations from a driver’s perspective and press a response button each time they identify a hazard (see Horswill & McKenna (2004) for a review). Typically, when using this type of paradigm, young-novice drivers identify fewer potential hazards than experienced drivers and they are also slower. However, some studies did not find differences in response time (see Borowsky, Shinar, & Oron-Gilad, (2010)for example).
    • Based on our thorough experience in analyzing these type of events we have developed a two-step analysis methodology. Dr. Yisrael Parmet will discuss the advantage and use of Survival Analysis in analyzing response times in driving related hazard perception paradigms on Friday, 31st of August 2012.

traffic scene clips - lead vehicle in an urban area  traffic scene clips - an urban area

This fall our team will be presenting at HFES 2012 Annual meeting.

  • “The use of a homogeneity measure to identify hazard perception abilities of novices and experienced drivers in a driving simulator”  Omri Yona, Avinoam Borowsky, Tal Oron-Gilad and Yisrael Parmet
    • Comparisons between young-novice and experienced drivers are beneficial for the development of both testing and training methodologies for young-novice drivers. Simulators are essential tools of driver assessment especially for novices. One way to look at the differences between driver groups is by examination of performance with regard to specific events. In addition, overall examination of performance across scenarios is important as it shows general patterns of behavior rather than specific ones. The common method to do so is by looking at the average of certain driving related measures or their variability. Using data derived from two hazard perception test (HPT) experiments in a driving simulator, we demonstrate how the use of a group homogeneity measure is more sensitive than the former two. Altogether, we demonstrate that consistently and regardless of road environment, experienced drivers manage their speed in a more homogenous way while novices act as inconsistent individuals.

image    simulated driving scenes - a residential area

  • “The Costs and Benefits of the “On-Thigh Vibrotactile Alerting System for the Cockpit” in High-Workload Environment” Yael Salzer and Tal Oron-Gilad
    • In the cockpit, an overloaded working environment, performance is prone to break down. Conveying crucial information through the tactile modality, which requires little to no additional effort, has been previously examined as means to improve performance and safety. Previously, we demonstrated the ability of the on-thigh vibrotactile alerting display to convey directional cues in the vertical plane. We hypothesized that tactile directional alerting cues would be beneficial in a visually loaded multi tasking environment. Two tasks were introduced simultaneously: a directional task where participants respond to directional cues (visual, tactile, or combination of both), and a memory recall task where participants identify, count and recall objects embedded in flight movies. Response time, accuracy and subjective workload were evaluated. Performance in the memory recall task and subjective workload were in favor of the combined tactile & visual configuration. No performance difference was found between visual and tactile & visual in the directional task. We concluded that the redundant tactile & visual configuration may allow operators to choose a strategy in which perceptual and cognitive resources are better utilized.

"on thigh" vibrotactile alerting system      Imagery of the visually loaded flight environment

  • “Display type effects in military operational tasks using Unmanned Vehicle (UV) video images: comparison between color and B/W video feeds” Yaniv Minkov, Ronny Ophir-Arbelle and Tal Oron-Gilad
    • The increased use of unmanned vehicles (UVs) in military environments requires development of guidelines to enable maximal compatibility between those technologies and users’ needs. Specifically, the way video feeds are delivered to dismounted soldiers may affect the utility of such information. This work follows previous studies on the type (e.g., size) of displays required by dismounted soldiers to process video feed from UVs in a variety of operational situations. Sixteen former infantry soldiers with no experience using UV video feed participated. Three display types were examined using color or B/W video feeds and three different operational tasks (identification, orientation and movement detection). Performance and subjective data were collected. Results showed an effect for display type only with regard to response time. Feed color and display type interacted. The 12″ Tablet black and white feeds produced the shortest responses.
    • Colored Images of a map and video from an unmanned ground vehicle  B&W images of a map and video from an unmanned aerial and ground vehicle

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