1Department of Community Health, School of Medicine, University of California, Davis, California 95616
2Department of Orthopaedic Surgery, School of Medicine, University of California, Davis, California 95616
In the past 25 years the number of registered motorcycles in the United States and California has increased about 1,000 and 1,111per cent respectively. In the same period the motorcycle collision death rate more than doubled. The lack of information on factors related to motorcycle collision injuries prompted our study in Sacramento County, California 1970. The purpose of this study was to examine time trends in motorcycle crash related deaths, to examine methodologic problems in the study of motor vehicle collision death rates and to evaluate the interrelationships between driver and vehicle factors which may contribute to the production of motorcycle injuries.
Information on deaths, population sizes and number of registered motorcycles was obtained from the U.S. Census, the National Safety Council, and California Departments of Motor Vehicles, Finance, and Health. Data on injured motorcycle drivers in Sacramento County, California were obtained from hospital records, California Highway Patrol, Sacramento City .and County police reports, self-administered questionnaires as well as driver records from the State Department of Motor Vehicles.
With the exception of 1974, the average annual increase in the ratio of registered motorcycles per 100,000 population in the U.S. since 1963 corresponded to an increase in crude death rate. A similar pattern between use of motorcycles and crude death rates is found also in California.
Stepwise discriminant analysis was used to identify interrelationships between factors associated with motorcycle collision injuries. The analysis indicated that for male drivers age was the single most significant factor related to motorcycle collision injuries. Other factors included; number of prior motorcycle crashes, number of prior motorcycle driving violations, frequency of motorcycle use, motorcycle drivers training, and height of the drivers. Among drivers more than 24 years of age, the discriminating factors included age, number of prior motorcycle crashes, larger engine size of the motorcycle, use of eye protection, more frequent use of motorcycles, more experience driving an automobile and drivers' training.
Prospective studies are clearly needed to show the precise levels of risk associated with the factors identified from this retrospective study of motorcycle crashes.