[Smog and traffic accident].

Some measures to counter car accident have been taken from various angels in recent times, while their epidemiological consideration has not sufficiently been given. The presentation here is a study on the latter problem. Three elements have to be taken into account when car accident is to be investigated epidemiologically; first, car traffic itself, secondly what is related to main constituent factors such as driver's mental and physical fatigue or difficulties, and thirdly what is concerned with environmental factors such as road conditions, traffic jam, and effect of lighting. Present subject has been concentrated on the significance of smog as one of the links of environmental factors in causing car accident. For this purpose authors took up car accidents which occurred within the circle of two kilometer at the central Tokyo, its center being the Japanese Meteorological Observatory where smog has been observed scientifically. Data are based upon the 1960•`1962 meteorological observation records field in the Japanese Meteorological Observatory and upon the traffic accidents records registered by policemen. Since smog occurs more frequent in January and December, available data were recorded in both months in 1960•`1962. The following are the results authors obtained in connection with the relationship between the smog and the car accidents. 1) The smog fosters car accidents during 3 hours from 9 to noon and 4 hours from 5 to 9 in the evening. 2) The higher is the effective temperatuae the higher is the frequency of car accident. 3) High rate of car-accident is observed between 17 to 21 hours below 30•‹ ET, and above 40•‹ ET high accident frequency is seen when there is no smog. At 30•‹ to 39•‹ ET high frequency is observed when there is no smog. While human injuries are more caused when ET is higher than 40•‹ with smog during 3 hours to noon, but during 4 hours around the sunset time it is high when smog is prevailling especially slight human injuries are seen oftener. 4) In terms of weather and effective temperature, the accident rate is higher when it is rainy and below 30•‹ ET. 5) The rate of accident is high when it is below 30•‹ ET, smoggy and rainy, and if it is above 40•‹ ET the rate is high when it is fine so far as it is smoggy, but under the same condition the rate of slight human injuries are high when it is raining. If it is 30•‹ to 39•‹ ET, slight human iujuries are oftener met when it is fine so far as it is smoggy.