The risk of car accidents caused by older adults having drivers’ licenses is increasing in the current super-aging society. Dementia and cognitive function disorders in older drivers inhibit safe driving. Moreover, cognitive functions decline with aging. Therefore, in Japan, high-risk strategies to deal with older drivers with suspected mild dementia have been developed. Future perspectives of preventing traffic accidents caused by older drivers are discussed based on the findings of studies, including national-wide cohort studies, on older drivers. In the discussion, the concept of prevention in public health studies, and the idea of hierarchical behavior control in psychology are considered, and models of human behavior for decreasing the risk of traffic accidents are evaluated.

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In the modern era, women have become accustomed to motor vehicle driving as a means of transportation. Compared to men, however, women are more susceptible to fluctuations in physical health concerning the menstrual cycle and circulating estrogen levels. Womenʼs health is a domain of health sciences with regard to female sexual and reproductive health. These topics have been primarily explored in terms of hormonal dynamics, but researchers are increasingly using comprehensive approaches for conducting an integrated analysis on the effects of different factors on womenʼs psychosocial health. In this review article, we aimed to identify and explore the factors influencing motor vehicle driving at each stage of a womanʼs life cycle, from the perspective of a womanʼs health. Driving behavior can be influenced by physiological changes corresponding to menstrual cycle. However, studies on traffic medicine and traffic science are yet to validate factors that are thought to contribute to traffic accidents from the womenʼs health perspective. We hope that future research will reconsider the findings of traffic safety research from the womenʼs health perspective, thereby focusing on driving-related factors unique to women.

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In Japan, the ratio of the middle-aged population is rapidly increasing, and the number of middle-aged drivers is expected to increase in the future, and urgent safety measures are desired. There are no studies that examine the visibility and responsiveness of the information inside and outside the car during actual driving and age factors. In this study, we focused on the speedometer as the in-car information in order to contribute to the design guideline of the in-car information display for middle-aged and elderly people. The purpose of this study is to clarify the relationship between visibility and responsiveness of middle-aged and elderly people when driving a car by comparing the results of the simulation experiment and the actual driving experiment. Simulator experiments were conducted with 20 young, middle-aged and elderly people under three conditions and four conditions, respectively, which correspond to the brightness in the evening, the brightness on a cloudy day and the brightness on a clear day without direct sunlight. The experiment was conducted under four conditions with 12 young and middle-aged people in total under clear skies. In both experiments, the reaction time with respect to the magnitude of the number displayed on the velocimeter in each condition was measured. The results showed that the reaction time of the speed display when driving a car was significantly longer in middle-aged people than in younger people, and that the age factor greatly affected the visibility and responsiveness of the information in the car during driving. The reaction time of the speed display should be shortened by the size of the speed display 25×50 mm （3°34’ viewing angle） for both young and middle-aged people. From the results of the simulator experiments, it was found that under the present experimental conditions, the influence of the illuminance factor on the visibility and responsiveness of the speed display was significantly smaller than that of the age factor or the size factor of the speed display.

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Inspection systems able to identify the speed of a vehicle were formerly developed. A video movie was used for one system and 2D animation was used for another. The abilities of young and elderly subjects were studied using these systems, which could reproduce the vehicle size and road environment, but could not completely reproduce binocular distance perception information unlike reality. Therefore, in this paper, we modified the system originally in 2D animation to 3D animation and tried a similar inspection. As a result, we clear that elderly subjects recognized vehicle speed in comparison with young subjects by mistake. This result was the same as in the 2D animation inspection.

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In recent years, traffic accidents related to impaired health have become an increasingly serious problem in Japan. The Dangerous Driving Causing Death or Injury applies when someone driving a motor vehicle is unable to do so safely owing to a health condition specified by a cabinet order related to certain diseases. Such diseases are likely to hinder the safe driving of vehicles and may lead to death or injury. The law concerning driving under such conditions is covered by the Act on Punishment of Acts Inflicting Death or Injury on Others by Driving a Motor Vehicle among other legislation. Health-related traffic accidents are caused by common health conditions as well as by particular diseases. There are difficulties in perceiving the risks conferred by changes in a driverʼs physical condition; however, accidents caused by such changes can result in severe injuries or fatalities. We studied 15 cases involving vehicle collisions in Japan caused by common diseases or symptoms, and we focused on criminal liability. The average age of the drivers was 51.1 ± 13.3 years; two-thirds of them were professional drivers. With regard to health impairment at the time of the accident, five drivers were suffering from the common cold and sneezing; two had influenza; and one had pharyngitis, abdominal pain, and aspiration. Of the 15 cases, eight were subjected to criminal proceedings: seven drivers were found guilty of Negligent Driving Causing Death or Injury; one case was dropped. The courts ruled that drivers suffering from common diseases or symptoms should avoid driving or halt their vehicles on becoming aware of their physical condition; the courts ruled that that should also be required of drivers suffering from particular diseases. Three drivers received prison sentences: because they were professional drivers, their employers could be held liable for accidents caused in the course of their employment. Thus, employers need to recognize the risk of health impairment by common diseases or symptoms; they should implement appropriate health measures to ensure the adequate functioning of the drivers they hire.

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The revised Road Traffic Law was enforced in Japan in March 2017 and cognitive decline has since been pointed out during driverʼs license renewal, thus the number of elderly people who visit hospitals has increased in Japan. The number of elderly people who visit our clinic for the purpose of preparing a medical certificate for renewing their driver's license is increasing, and we investigated the current situation. During the 29 months from March 2017 to July 2019, 290 patients visited our clinic. Among them, a decline in cognitive function while renewing their driver's license was noted in 25 and they consulted for the purpose of preparing a medical certificate. We examined the cognitive function tests performed by the Prefectural Public Safety Commission, the neuropsychological tests（HDS-R, MMSE, FAB, CDR, TMT, MoCa-J）performed at our clinic, and their current driving status. The 25 patients comprised 22 men and 3 women, with an average age of 80 ± 4.1 years and average educational history of 10.5 ± 2.7 years. The median total score of cognitive function tests conducted by the Prefectural Public Safety Commission was 35 points. In addition, the median scores of neuropsychological tests performed at our clinic were HDS-R: 17, MMSE: 21, FAB: 10, and CDR: 0.5 for 14 patients, and CDR: 1.0 or higher for 11 patients. The TMT-A score was lower than the age average for 8 subjects（out of 25）and the TMT-B score was lower than the age average 18 for（out of 21）. As a result, three of the 25 patients were diagnosed with mild cognitive impairment and continued driving, and 22 were diagnosed with dementia or suspected dementia, and voluntarily returned their driving license. Interviews with the patients revealed that their family noted their cognitive decline in 64％, but they only noted a high accident risk of driving in 24％. In Fukui Prefecture where our clinic is located, elderly drivers need cars. Some of the elderly drivers can drive with a low accident risk even if cognitive function is reduced. On the other hand, in many cases, their family members do not notice that they have dementia; therefore, it is necessary to sufficiently interview them regarding daily life and to examine cognitive functions in many fields to determine whether they can continue driving.

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