From 2018, D-Call Net which links AACN（Advanced Automatic Collision Notification）and doctor helicopters was started in Japan. However, D-Call Net is only for doctor helicopter base hospitals and no information is provided to hospitals with only doctor cars. Therefore, by extending the information service range of D-Call Net to hospitals with only doctor cars, it is possible to reduce the number of deaths and after-effects of road traffic accidents. The purpose of this study is to investigate the doctor car operation conditions and estimate the response rate for the number of traffic fatal accidents in order to confirm the lifesaving effect when D-Call Net was applied to a doctor car. First, we investigate the operation conditions using internet, hearing and literature surveys for medical institutions with doctor car or helicopter. Next, based on the survey results and ITARDA macro accident data, we estimated the doctor car response rate for traffic fatalities including the doctor helicopter effect. As a result, in 157 hospitals with doctor cars, the operating hours is unknown and their doctor car may be dormant. In addition, the main causes of dormant are operating costs and securing human resources such as doctors and drivers. On the other hand, we found that the current doctor car response rate for traffic fatal accidents is 5.7％ and it is lower than 22.9％ for doctor helicopter response rate. However, if the doctor car operation time is changed to 24 hours/365 days and all surveyed hospitals（338 facilities）have doctor car, the response rate improved to 45.1%. This indicates that the doctor car has high potential in response rate for traffic fatalities.

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In 2018, rear-end collisions accounted for 35％ of traffic accidents between vehicles in Japan and they accounted for the greatest proportion. Moreover, multiple collisions accounted for 13％ of rear-end collisions in Japan from 2007 to 2012. In a rear-end collision, sometimes a driver’s foot in a struck vehicle comes off the brake pedal and this may cause multiple collisions. A post-crash safety system is one of the technologies used to ensure post-crash safety. It assists the driver to stop the vehicle by operating an automatic brake after rear-end collision, so that prevent multiple collisions can be prevented. Practical use of this system has already begun in Europe. Based on previous research, a post-crash safety system has the potential to avoid multiple collisions; however, the system has not yet found practical use in Japan. The purpose of this study is to elucidate the mechanism of brake discontinuation and the collision condition that causes brake discontinuation in a rear-end collision. First, the behavior of a driver’s lower leg when a rear-end collision occurred was analyzed based on physical crash tests using a K-car. In addition, the relation between the brake operation of a driver and the speed of a struck vehicle when a rear-end collision occurred was analyzed based on physical tests and a drive recorder database. The results confirmed that the backward movement of a driver's ankle after a rear-end collision, which depends on the speed of a struck vehicle, affects the brake operation.Second, a formula was derived to estimate the striking speed when the brake discontinuation probability of a struck vehicle after a rear-end collision was 99.9％ by logistic regression analysis. Based on this formula, the striking speed that caused brake discontinuation in the event of a rear-end collision between a normal passenger car and a K-car was identified as 10.2km/h. Also, the striking speed that caused brake discontinuation in the event of a rear-end collision between cars with the same mass was identified as 15.3km/h. Moreover, the frequency of rear-end collisions at both these striking speeds is high.Therefore, a post-crash safety system operating at these speeds is an effective measure to prevent multiple collisions in Japan.

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In recent years, there have been sporadic incidents of vehicle collisions caused by the elderly. We studied 26 cases involving vehicle collisions caused by elderly drivers, subsequently looking into their criminal responsibility. The average age of the drivers was 76.0±7.4 years old. Seven drivers had health conditions such as dementia, epilepsy, diabetes, and heart disease among others. Eight cases were caused by the erroneous tread of a brake pedal and the accelerator pedal. Twenty drivers were prosecuted on a charge of negligent driving, and two were prosecuted on a charge of dangerous driving. Most of the traffic accidents caused by the negligence of the elderly drivers were exempted from prosecution in Japan. However, in the case of a driver who caused a fatal accident, he was charged with negligent driving for having failed to exercise due care, coupled with his malicious intent to violate the traffic laws. As for traffic accidents causing serious damage, the court judged that their violation of duty care was serious and malicious. Because of this, the drivers were handed prison terms. Even though old age or a long good driving record were considered in the determination of the appropriate punishment for the elderly drivers, these still did not extinguish their criminal responsibility for negligent driving. On the other hand, on the trial regarding dangerous driving, their old age was considered as an exempting circumstance. Revocation of the driver’s license was the punishment of an elderly person with dementia, not being able to avoid the collision. Learning from these cases, it is necessary to provide a support system which instills awareness in elderly drivers that their driving abilities are declining. They should not be overconfident about their own good driving records. Moreover, companies should be required to take further vehicular safety measures for their older employees in order to prevent these road mishaps.

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【Introduction】The incidence of severe injuries caused by the extensive vehicle collisions has decreased owing to the legislation of wearing a seatbelt for all vehicle passengers and improvement of vehicle safety equipment. However, body injuries due to seatbelt itself have been increased. 【Objective】To clarify the patterns and severities of body injuries due to seatbelt compression, retrospective analysis was performed. 【Material & Methods】A total of 14 cases of trunk injuries due to a seatbelt compression in our critical care center from April 2013 to May 2018 were reviewed. 【Results】The average age of all patients was 49 years old. Ten patients were vehicle drivers and 3 were front seat passengers. Among 10 patients with injury severity score of 9 or more, 4 patients had severe injury in the neck, thorax, or abdomen, and 6 patients suffered from multiple severe injuries in the neck, thorax, and/or abdomen. For 4 patients, because the seatbelt was considered as inappropriately positioned, they suffered from mesenteric injury and fascial hemorrhage in the abdominal wall owing to the compression of the abdomen by lap belt or subcutaneous hemorrhage of the neck owing to the compression of the neck by shoulder belt. 【Conclusion】To check the seatbelt using situation is important for a correct diagnosis of traffic injurie of motor vehicle passengers. Even if the injury severity is considered as minor, patients should be carefully followed for a while after admission.

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A Minicar is a micro mobility, that is expected to have widespread use in the future. It is suitable for the transportation of elderly people and for deliveries because of its small size and single seat. However, collision safety of a minicar has not been reported. Because a minicar is smaller than small cars, so it is difficult to secure an enough crashable zone. Therefore, in frontal collision of a minicar, the cabin may be largely deformed and the steering wheel collide with the occupant. Occupant injury occurs because of the collision with the steering wheel. In previous studies, a full frontal rigid barrier impact test using a minicar was conducted （initial speed 55 km/h） and the problem of minicar in frontal collision were clarified. The steering wheel retreated and collided with the occupant because of the large deformation of the body frame. Therefore, occupant face a high risk of injury. Therefore, in this study, a full frontal rigid barrier impact test was simulated using the finite element model reproducing the front body frame and chassis structure of the experimental vehicle, and the multi-body model reproducing the interior parts and the occupant. To reduce the occupant injury by improving the body frame structure, deformation of the cabin was suppressed by increasing the rigidity of the front frame. On the other hand, the maximum acceleration was increased because of the high rigidity of front frame. Therefore, the maximum deceleration was suppressed by equipping the crushable box. In addition, the restraint force of the seat belt was adjusted to avoid the collision between the steering wheel and the chest by adding a seat belt pretensioner and a force limiter. Two consecutive improvement to the body structure and occupant restraint method were enforced, and then chest deflection and HIC₃₆ as a head injury index reduced below injury criterion.

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[in Japanese]

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