We retrospectively analyzed forensic autopsies of the motor vehicle drivers. Thirty-three victims had died of disease while driving a vehicle（Sudden death while driving）. Eight victims died of injuries, but had not attempted any avoidance maneuvers immediately before the accident（Traumatic death without avoidance maneuvers）. In both groups, more than 70% of victims suffered from any disease, hypertension, cardiac or aortic disease, and hyperlipidemia. Injury severity score was significantly higher in the victims of “Traumatic death without avoidance maneuvers” than those of “Sudden death while driving”（37.0±2.3 vs. 4.7±7.8, p‹0.001）. When the drivers suffer from sudden-illness while driving vehicles, most of them are unable to avoid collisions without attempting avoidance maneuvers. There have been some victims who suffered from moderate to severe traffic injuries owing to the undiagnosed sudden-illness while driving a vehicle. For the drivers with traffic injuries, medical personnel have to find the latent sudden-illness which might disturb the driving with expanding the scope.

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Many convex mirrors are installed at non-signalized intersections, but two mirror types are often mixed. A double mirror is a set of two mirrors on one pole, and a pole is installed on just one side of an intersection. This type of mirror will reflect the right road situation in the reflect right mirror. A single two-sided mirror is installed on one pole, and one pole is installed on each side of the intersection. This type of mirror will reflect the right road situation in the left mirror. Moreover, right and left are reversed in the mirror image. Therefore, it is difficult for drivers to determine the position of reflected vehicles in the intersection or which direction the reflected vehicle will go. Twenty-four persons participated in this experiment to determine the difficulty of these tasks. Subjects pointed out the position and direction of the reflected vehicle, and their reaction time and error ratio were measured. The reaction time to detect the vehicle position, the reaction time to detect vehicle direction of travel, and the error ratio were all significantly greater for two-sided mirrors than for double mirrors.

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Determining collision points is quite important for the investigation of accidents between pedestrians and vehicles. Firstly, because the position of the pedestrians, for example if they are walking on a pedestrian crossing or not, has a great influence on determining if drivers are responsible for accidents. Secondly, because from collision points we can estimate the speed of the striking cars. One of the methods to determine collision points is to carefully observe the skid marks on the road. When vehicles hit pedestrians after applying the brakes, the skid marks sometimes bent slightly at the collision points. We verified with crash tests using dummies and the computer simulation PC-Crash that skid marks begin to bend at a point 0 to 2 meters past the collision points. Hats or caps of hit pedestrians are sometimes found on the crash site. We verified with crash tests using dummies that the hats or caps tend to fall near the collisionpoints. In the tests, caps come off from the dummies heads at the moment of the collision and fall vertically. However when caps come in to contact with the car body such as the roof edge while falling, the caps can fly a few meters away from the collision point. Crash tests also show that umbrellas held by pedestrians tend to fall near the collision points.

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To diagnose the unconsciousness while driving a vehicle, we investigated the driving posture immediately before the collision. Computer simulations were performed based on forensic autopsy cases in which drivers had not taken avoidance maneuvers. MADYMO 7.0 was used to reconstruct the accidents. Two out of 267 autopsies related to traffic accidents were chosen. The drivers, who had operated small passenger vehicle, died of aortic injuries. Focusing attention on the pre-crash drivers’ driving posture, we reconstructed the driver kinematics during crash based on the accurate injury information described in autopsy examples on the computer simulation and analyzed them. As results, we revealed the pre-crash drivers’ driving posture and the features indicating that these drivers were in states of unconsciousness just before the crash. Our analysis contributed to the diagnosis that the driver had lost consciousness during driving and could not avoid the collision. Reconstruction of driving posture before the accident by computer simulation model might be useful for the elucidation of the actual cause of the motor vehicle collisions.

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