5.How many people can be saved by the use of seat belts?
  Let's look at how the number of fatalities would be reduced if all vehicle occupants were to use seat belts. In 2001, the number of casualties was 737,577; the number of fatalities was 3,711; the numbers of casualties among occupants wearing seat belts and among occupants not wearing seat belts were, respectively, 637,352 and 91,689; and the numbers of fatalities among such occupants were, respectively, 1,377 and 2,167. Accordingly, one out of about 462 occupants wearing seat belts was fatally injured, while one out of about 42 occupants not wearing seat belts was killed.
  Since the seat belt use rate was 86.4% in 2001, one percentage point corresponds to 7,376 people (637, 352/86.4%). Assuming, therefore, that the 7,376 people who did not wear seat belts were to use them, the number of fatalities would be reduced by about 158 people. This is shown diagrammatically in Figure 8. Moreover, if the seat belt use rate could be raised to 90%, about 568 lives would be saved, while a 95% rate would result in about 1,358 lives saved.

Fig.8 Estimated Number of Fatalities by Seat Belt Use Rate (Estimated Reduction in Fatalities If Seat Belt Use Rate Were 1% Higher than Current 2001 Rate, and If Rate Were 90% or 95%)

  Incidentally, the seat belt use rate and fatality rate vary depending on seating postition. What is more, a variety of factors affect the degree of personal injury; namely, the collision forces working on the vehicle, the age of the occupants, and so on. We therefore eliminated the effects of these factors and quantitatively analyzed only the effect of seat belt use. Trying to standardize conditions as much as possible, we looked at occupants in accidents involving ordinary passenger cars with bonnets, in which the front of the vehicle was struck in either a head-on or rear-end collision. In our analysis, however, we added together the number of fatalities and the number of serious injuries.
  The total data of the 6-year period from 1995 to 2000 show that there were 4,110 drivers wearing seat belts and 2,141 drivers not wearing seat belts who died or were seriously injured in accidents. If we count in the number of slightly injured and uninjured drivers, we get a total of 31,692 drivers not wearing seat belts. If all these people had used seat belts, the number of fatalities and serious injuries would have been 49% less, that is, 1,102 drivers. Similarly, seat belt use would have reduced the number of fatalities and serious injuries among front seat passengers by 42% and among rear seat passengers by 45%, as is evident from Figure 9.
  This confirms that seat belt use will lessen the degree of injuries of vehicle occupants, regardless of their seating positions.

Fig.9 Estimated Number of Fatalities and Serious Injuries of Occupants Wearing Seat Belts by Seating Position (6-Year Total from 1995 to 2000)

6.Should we use seat belts only for our own sakes?
  In accidents in which the front of a vehicle is struck, the rear seat passengers are thrown toward the front seats, so the injuries of front seat occupants can be more severe. Accordingly, the use of seat belts by rear seat passengers in such accidents can lessen the degree of injury of the front seat occupants.
  Let's look at the number of fatalities and serious injuries among drivers and front seat passengers, selecting accidents involving vehicles with rear seat passengers in which all the occupants were injured.
  There are cases where drivers and front seat passengers were seriously injured even if the rear seat passengers were wearing seat belts. As is evident from Figure 10, however, in vehicles with rear seat passengers wearing seat belts, the number of fatalities and serious injuries among front seat occupants can be reduced by 25% in the case of drivers and by 28% in the case of front seat passengers.

Fig.10 Estimated Number of Fatalities and Serious Injuries of Front Seat Occupants, with Rear Seat Passengers Wearing Seat Belts (Analysis Based on Total Accidents of 6-Year Period from 1995 to 2000 Involving Ordinary Passenger Cars with Bonnets)

7.What about these reports of occupants being thrown from vehicles and saved?
  During the 3-year period from 1999 to 2001, 3,389 occupants were injured by being thrown from vehicles, and of these, 988 died (Figure 11). Although this included occupants who used seat belts, the majority did not use seat belts.
  Figure 12 compares the component ratio of fatalities (fatality rate) between cases in which occupants were injured by being thrown from vehicles and cases of occupants injured other than by being thrown from vehicles. Once injured, occupants who were thrown from vehicles were more likely to die than those not thrown from vehicles, and this was particularly true in cases where seat belts were not used. The use of seat belts is therefore the absolute condition for preventing occupants from being thrown from vehicles.

Fig.11 Comparison of Component Ratios of Occupants Thrown from Vehicles Who Used Seat Belts and Those Who Did Not Use Seat Belts (3-Year Total from 1999 to 2001)

Fig.12 Comparison of Fatality Rates of Occupants Thrown from Vehicles Who Used Seat Belts and Those Who Did Not Use Seat Belts (3-Year Total from 1999 to 2001)

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Institute for Traffic Accident Research and Data Analysis (ITARDA)