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The number of elderly drivers is increasing in Japan and ensuring the safety of elderly drivers is becoming an important issue. The authors previously conducted an analysis of the characteristics of accidents and traffic violations by elderly drivers based on the number of accidents in which they were rear-ended. This method was used in order to exclude the influence of driving frequency. As a result of that analysis, it was found that the likelihood of violations committed by elderly drivers was not particularly higher than in other age groups, while the likelihood of accidents caused by them was higher. The risk of causing an accident was judged to be about two times higher in elderly drivers than in the 35-44 year age group. However, the methodology presupposed that collisions in which a driver is rear-ended are accidents that occur randomly, and that they occur with the same probability in each age group.

The number of elderly drivers has been increasing in Japan with the rapid progress of the nation's population aging. Securing safety for elderly drivers is an important issue in Japan. In this paper, authors conduct analysis on characteristics of accidents and violations caused by elderly drivers based on data for 2009. As there is a tendency that elderly drivers generally have less opportunity to drive vehicles than younger drivers do, it is necessary to conduct this analysis considering driving frequency when making comparison among age groups. Then, we calculated the normalized ratio (odds ratio) based on the number of rear-ended accidents in order to exclude the influence of driving frequency. As a result of the analysis, it was found that the likelihood of violations committed by elderly drivers was not particularly higher, while the likelihood of accidents caused by them was higher than younger drivers.

This paper deals with an investigation on whether the change in the viewing environment at dusk has a connection with the occurrence of traffic accidents by statistical analysis of data on traffic accidents in Japan. In this paper, dusk is considered to be a time period of civil twilight which is about 30 minutes in Tokyo. The target area is limited so that the time period for dusk would be basically the same time. As a result, the author could not recognize a tendency for traffic accidents to occur with especial frequency in the period of dusk. In addition, there was analysis in terms of the ages of the drivers (drivers in their 20s, 40s and 65 years or over). Judging from data on traffic accidents, the author could not confirm a tendency toward more frequent traffic accidents at dusk in any of the age groups, including drivers of advanced age.

Head-up displays (HUDs) require drivers to perceive double images simultaneously, that is, the scene to the front and display images, and this simultaneous viewing of two objects may cause cognitive confusion during driving. In this paper, we discuss some factors that determine the appropriate area for HUDs. First we discuss the feeling of troublesomeness with consideration of eye movements during driving. Secondly, we investigated the situation wherein the driver in a trailing vehicle perceives the stop lamps of a lead vehicle. Upon these considerations, we conclude that in the vertical direction the area under 4 degrees below the horizontal line would be a safer display area.

When a driver views the display device, there are two ways to read the information displayed: repeatedly diverting his attention to the display device for short periods of time or reading the information through, all at one time. The authors investigated differences in the amount of information retained for both of these reading methods by carrying out experiments indoors. This experiment showed that even when the amount of time that the subject was actually viewing the display was the same, the amount of data acquired by the subject from reading the display repeatedly was greater than the amount of information acquired by reading the display through at one time.

The authors have carried out two types of tests regarding head-up displays (HUDs) for the purpose of determining the relationship between display position and a feeling of troublesomeness for the driver. The first test was a basic experiment to evaluate how troublesome the HUDs were to an observer sitting in a chair outdoors. The collected data was used as the basis for carrying out approximation by means of two-dimensional normal distribution. In the second test, the observer was actually in a car and a mock-up HUD making use of clear film was used to carry out the experiment in investigating how the feeling of troublesomeness changed depending on whether the vehicle was in a stop state or in a moving state. Compared to a stop state, the results in a driving state showed a shift toward the left side for the distribution of a feeling of troublesomeness. The reason is probably because the distribution of the line of vision of the driver moves toward the left when driving in Japan.

When a driver looks at a display screen for a navigation system or the like, they are not able to pay adequate attention in front of them. By proposing a calculation method, we stochastically analyze how much noticing of danger ahead is delayed and how much the braking operation is delayed. The validity of this method is verified by the experimental data. We reveal that it is possible to quantitatively infer the delay in the braking operation due to the driver looking at the display screen by comparing the calculated results with the data for when the driver is not looking away.

If the distance from the driver to the virtual image of a head-up display is short, when the driver is viewing the scenery ahead, there is perception of a HUD double image by the left and right eyes. This paper describes an indoor experiment carried out to analyze the relationship between the feeling of troublesomeness of the HUD and binocular vision. In the case of a HUD displayed to the right side from center, of the double image, it is clear that it more strongly receives the influence of the image by observation with the right eye. Conversely, in the case of a HUD displayed to the left side of center, of the double image, there is a stronger influence of the image received by observation with the left eye. This paper also involves analysis of the influence of the preferred eye on a feeling of troublesomeness.