The study of characteristics of visual attention in depth of drivers in traffic environment 交通環境における運転者の奥行き視覚的注意特性に関する研究

博士論文

The number of traffic accidents keeps increasing with increasing of the number of private cars and the improvement of road traffic environments although death number of traffic accidents keeps decreasing over the recent years. There were a lot of factors for the traffic accidents, those factors that are directly related to people-the so-called “human errors”-has been examined by considering a car to be a cooperative human-machine system and through the analysis of about 300 road traffic accidents by the Institute for Traffic Accident Research and Data Analysis (ITARDA). When human errors are grouped into three categories, namely, cognitive errors, judgment errors and operation errors, they are found to constitute 47%,40%, and 13 of the total, respectively, meaning that cognitive errors and judgment constitute about 90% of all human errors. In addition, a lot of death numbers in the twilight condition have been reported. There are several reasons for the human errors; one of the main reasons is the effect of traffic environment (including car exterior and interior environment) on safety driving. Another primary reason is the effect of the visual function of drivers on operations of drivers.

With the popularization of the information prompt instruments in the car interior like automobile navigation system and speedometer etc., drivers obtained more and more information from the screen display. It is important the effect of the expression color of the information prompt instruments in the car interior on the visual attention of drivers. So, it is very important to reveal the vision attentional characteristics of drivers. However, characteristic of depth attention of drivers remained unclear, only a few studies addressed the effect of the environmental illuminance in car exterior and the information prompt instruments in car interior on the visual attention of drivers. We designed an attention measurement system to conduct four experiments in order to research the attentional characteristics of drivers in the present study.

The environmental illuminance in car exterior can be divided into three categories: The bright, twilight and dawn. There are various kinds of color combines between the information prompt instruments in car interior and the traffic environment in car exterior. In order to ensure traffic safety and to obtain more visual information, drivers have to switch continually their visual attention between the objects presented in front of drivers because various kinds of traffic environments are changing continually during driving. The present study consisted of the following four parts:

(1) A study on characteristics of attention in depth of young subjects in changing supposed environmental illuminance. The experimental environment illuminances were: bright (480-680 lx) and twilight (95-135 lx) conditions. Subjects were fifteen students served as participants, whose mean year was 21.8 years old. The subjects must make a quick response according to the information presented beforehand at the targets location. Three within-observe variables were used: cue validity (Valid: V, Invalid: I, Neutral: N). 65% of all trials were Valid, 15% were Invalid and 20% were Neutral. The experimental results suggested that the attentional characteristics of subjects were influenced not only by the vision function of subjects, but also by cue validity. Reaction time was shorter in the valid, and longer in the invalid. In addition, there was an effect of environmental illuminance on response lag in low illuminance condition, and the response lag depended on the shifting distance of the attention in depth. (Bright: 480-680 lx, twilight: 95-135 lx and dawn: 5-8 lx)

(2) A study on characteristics of attention in depth of subjects simulated low-vision in changing supposed environment illuminance. The experimental environment illuminances were: bright (480-680 lx), twilight (95-135 lx) and dawn (5-8 lx) conditions. Subjects were fourteen students served as participants, whose mean year was 24.9 years old. The results suggested that the attentional characteristics of subjects were also influenced by the environmental illuminanc. In particularly, reaction time was shortest in the dawn condition than in the bright and twilight conditions, and showed that there is an effect of low environmental illuminance on response of subjects.

(3) A study on characteristics of attention in depth of older subjects in supposed bright condition. The experimental environment illuminance was: bright (480-680 lx) condition. Subjects were fifteen older peoples served as participants, whose mean year was 63.9 years old. The results suggested that their reaction times were obviously longer than young subjects.

(4) A Study on characteristics of attention in depth in changing cue duration and targets color in supposed traffic environment. The experimental cue durations were: 600 and 1000 ms, and color of cue and targets were red and green under two observing conditions (static and dynamic). The results suggested that it was evident the effect of color on the response lag when the color of cue and color of targets was not consistent.

In present study, the visual attention characteristics of young, low-vision and older subjects are examined by changing peripheral environmental illuminance and color combination of cue and targets. Four experiments are conducted. The results of the environmental illuminanc experiments suggest that reaction time of the subjects with high visual adaptability is shorter than the subjects with low visual adaptability in twilight condition, this results show that the subjects with low visual adaptability have a response lag in twilight condition, the direction of switching attention of subjects result in this orientation to response lag. Response of subjects with low visual adaptability is slower than subjects with high visual adaptability when the attention distance is greater. The results of the color combination experiments suggest that the asymmetry of attention is small in cue being red than that in cue being green, on the other hand, the reaction time is shorter in targets being red than that in targets being green in invalid condition.

In conclusion, danger tendency of drivers is exposed in traffic environmental illuminance change in this study. To be engaged in traffic safety education, according to those research results, we should expound visual attention characteristics to drivers, even try to append these finding into teaching pamphlet in order to ensure traffic safety and to decrease traffic accidents.