3.0 REVISING ESTIMATED EFFECTIVENESS

Since 1987 there have been changes in the design and materials used to manufacture motorcycle helmets. Has the effectiveness of motorcycle helmets in reducing fatalities also changed and, if so, is the effectiveness higher or lower than it was in 1987?

3.1 UPDATING THE DATA

Table 4 shows the annual and total fatality ratios recalculated using the ten most recent years of FARS data to reflect technological changes since 1987. The ten-year time period was selected in order to increase the number of cases available and to control for the effects of years with outlying data. As was the case for the 1982 through 1987 data, the individual years are shown for comparison purposes only -- the overall totals were used to calculate effectiveness.

Table 4
Rider/Passenger Fatalities in Motorcycle Crashes*
By Helmet Use Status 1993-2002

Source: National Center for Statistics and Analysis, NHTSA, FARS 1993-2002
* Crash must involve both a rider and a passenger on the same motorcycle.

Table 5
Helmet Use Effectiveness (Percent) For Motorcycle Riders
and Passengers 1993 through 2002

Source: National Center for Statistics and Analysis, NHTSA - FARS 1993-2002

In Table 5, a motorcycle helmet effectiveness of 39 percent was calculated using the cumulative data from 1993 through 2002, compared with the 29 percent calculated with data from 1982 through 1987. As in the 1989 report, multiple years of data were used in order to control for the small numbers of crashes meeting the criteria in any particular year. In the case of riders accompanied by unhelmeted passengers in 1997, for example, 9 helmeted riders and 5 unhelmeted passengers were killed in fatal crashes involving both a rider and a passenger. This may indicate not only that more motorcyclists are wearing helmets, but that passengers accompanying riders wearing helmets are more likely to be helmeted as well. One problem in using the paired comparison method to estimate effectiveness of protective equipment is that survivors may tend to exaggerate their use in order to avoid being cited for non-use. In the case of motorcycle helmets, this effect is offset both by the high visibility of motorcycle riders in comparison with motor vehicle occupants and the fact that only 20 states and the District of Columbia require all riders to wear helmets. There are currently 3 states that do not require helmets and 27 states that require helmets only for certain classes of riders. Effectiveness is used to estimate the number of lives saved as follows:

Lives Saved = Fatalities _Helmeted * Effectiveness / (1-Effectiveness)

And the potential number of lives saved as:

Potential Lives Saved = (Fatalities _Total + Lives Saved _Total) * Effectiveness

Tables 5 and 6 show the numbers of lives saved and the potential lives saved in 2002 using 29 percent effectiveness (Table 6) and effectiveness as derived from more recent data (Table 7).

Table 6
Motorcyclists Saved by Helmets In 2002 Using Un-weighted Average for Total Effectiveness (Effectiveness Based on 1982-1987 Data)