banner of Methodology for Determining Motorcycle Operator Crash Risk and Alcohol Impairment

3. Detailed Report of Discussion

General Issues

General Exposure Data

For various reasons, it may be beneficial to obtain data on how many motorcyclists are riding on which roads, the demographic characteristics of those riders, and how many miles per year they are riding. These data might be obtained from the following sources:

  • Motorcycle sales data—Data are available concerning the number of motorcycles sold in the United States every year, which would help provide a rough estimate of the number of motorcycles which may be on the road. These data would not be particularly helpful in understanding the number of miles ridden or demographic data for riders.  These data would not reflect miles ridden on older motorcycles or miles ridden by non-owners.  Also, many motorcyclists own more than one motorcycle, which potentially skews the data.  
  • Motorcycle registration data—Registration data contain demographic data and data on the nature of the motorcycles themselves. Registration data can do little to tell us how much these motorcycles are being ridden. Issues that cloud the connection between registration data and exposure data include the fact that some motorcycles may not be registered (though unregistered motorcycles are probably untagged and therefore not ridden on public roads); some riders own and register multiple motorcycles (but can ride only one at a time); the registered owner may not be the person riding a motorcycle.
  • Motorcycle license data—All States require motorcyclists to have a separate motorcycle license or endorsement. However research shows that there is a high proportion of riders who have not gotten a motorcycle license. There is also possibly an equally high population of licensed motorcycle riders who do not ride. Because there is a correlation between riding unlicensed, drinking and riding, and riding un-helmeted, there would be methodological problems inherent in any study that attempted to understand the effects of drinking and riding using only licensed riders.
  • Federal Vehicle Miles Traveled (VMT) Data—Data are available on yearly VMT through the Bureau of Transportation Statistics of the Federal Highway Administration.  It has been suggested that VMT for motorcycles is being underestimated.
  • Highway usage data—States are required to keep data on the number and nature of vehicles using major highways. These may give some insight into the number of motorcycles on these roads and the numbers of miles being ridden. These data focus on highways, which are not necessarily where most motorcycles are being ridden, nor are they where most crashes are taking place.
  • Travel demand data—States keep data on the extent to which roads are being used so that forecasts can be made of future needs and the effects of traffic on the environment can be determined. These data may not contain information on how much of this traffic is comprised of motorcycles.
  • Surveys of motorcyclists—It may be possible to determine all of this information by surveying motorcyclists. The advantage of doing so would be that a large amount of information could be obtained concerning the riders. The disadvantages would be the disadvantages of survey research discussed above, plus the fact that all data would be self-reported (self-reported exposure data may not be accurate).
  • Roadside counts—One way to determine the number, and to some extent, the nature of motorcycles on a particular roadway would be to stand beside the road and count motorcycles. Estimates of motorcycle size and type (e.g., sport bikes, cruisers) could be made. Determination of helmet status (e.g., no helmet, novelty helmet, full-face helmet) could also be made. Determination of age, race, and gender may be difficult depending on helmet status.
  • Videotaped footage of traffic from traffic cameras—Many States and local jurisdictions have traffic cameras that are capable of being used to videotape roadways. This would be similar to surveying from the side of the road except that roads would be limited to (generally) larger roads, and the point of view would be farther away, which would make the collection of some data difficult or impossible.
  • Insurance company data—Insurance companies keep records that may contain information on number of motorcycles in a household, number of riders and percentage of use of each motorcycle by each rider. Data would also include demographic data and may include crash data. Insurance companies do not generally make data available for research purposes and the data are often not sufficiently detailed for research purposes.