Effectiveness of Antilock Braking Systems in Reducing Fatal Motorcycle Crashes

The effect of antilock braking systems (ABS) on motorcyclist fatal crash risk in 2005-06 was studied by comparing fatal crash rates per registrations of motorcycles with and without ABS. Study motorcycles included those for which ABS was optional equipment and could be identified as present by the model name. Fatal motorcycle crashes per 10,000 registered vehicle years were 38 percent lower for ABS models than for their non-ABS versions. INTRODUCTION Annual motorcyclist deaths in the United States have more than doubled, from 2,077 in 1997 to 4,697 in 2006 (Insurance Institute for Highway Safety, 2008), and motorcycle registrations have increased by about two-thirds, from 5,167,693 in 2000 (earliest year for which data are available) to 8,642,243 in 2006, according to data from R.L. Polk and Company. Many factors contribute to motorcycle crashes, but improper braking was identified as a major pre-impact factor in a study of motorcycle crash causation (Hurt et al., 1981) and again, 20 years later, in the Motorcycle Accident In-Depth Study (MAIDS) (Association of European Motorcycle Manufacturers, 2004). Operating the brakes on most motorcycles is much more complicated than on four-wheel vehicles. Most motorcycles have separate controls for the front and rear brakes, with the front brake usually controlled by a lever on the right handlebar and the rear brake controlled by a pedal operated by the rider’s right foot. During braking, a rider must decide how much force to apply to each control. As with other types of vehicles, much more deceleration can be obtained from braking the front wheel than from braking the rear wheel. Motorcycles are inherently less stable than four-wheel vehicles and rely on riders’ skills to remain upright during extreme maneuvers such as hard braking. Braking too hard and locking a wheel creates an unstable situation. Locking the front wheel is particularly dangerous, with loss of control being almost certain. A locked rear wheel is more controllable but still can lead to loss of control if the rider simultaneously tries to steer the motorcycle, as in an emergency avoidance maneuver. However, in an emergency requiring full stopping power, riders concerned about wheel lock may be reluctant to apply full force to the brakes, particularly to the front brake. Both Hurt et al. (1981) and MAIDS (Association of European Motorcycle Manufacturers, 2004) had examples of both loss of control due to wheel lock and failure to adequately brake. Although proper braking practices can be taught, rider training courses have not been shown to be effective in reducing motorcycle crashes (Mayhew and Simpson, 1996) or have provided mixed results at best (Billheimer, 1998). In an effort to address the issue of under-braking (especially the front wheel), manufacturers have developed braking systems that essentially link the front and rear brake controls. These systems, collectively referred to here as combined braking systems (CBS), apply braking force to