The age distributions of the fatally-injured and non-fatally injured bicyclists in the study sample are shown in Figure 4. (It should be noted that accident frequency is plotted for two-year age intervals.) Beginning at age four, accident frequency rises steadily to the age of 12 and remains at this high level through the age of 15. Thereafter, accident frequency declines dramatically and remains at a relatively low and constant level for ages beyond 30 years. The general shape of the curves for fatal and nonfatal accidents is similar, but fatal accidents are more frequent among the very young and the very old bicyclists. About 4.5% of the fatal cases involved a bicyclist younger than six years of age, whereas only two percent of the non-fatal cases involved a bicyclist younger than six years. Similarly, it can be seen that 18.2% of the fatal cases involved a bicyclist older than 35 years of age, and only 4.2% of the non-fatal cases involved a bicyclist older than 35 years. Although not shown in Figure 4, over 10% of the fatalities involved a bicyclist older than 55 years and three percent involved a bicyclist older than 75 years of age. It is of interest to note that the age distributions shown in Figure 4 are quite similar to the age distributions found in a number of other studies of bicycle/motor-vehicle accidents, including studies by: the American Automobile Association (1973), the California Highway Patrol (1974), the Virginia Department of Highways (1974), Walsh and Watt (1974), and the Washington State Patrol (1973).