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Several sources report simple equations for calculating the lean angle required for a motorcycle and rider to traverse a curved path at a particular speed. These equations utilize several assumptions that reconstructionists using them should consider. First, they assume that the motorcycle is traveling a steady speed. Second, they assume that the motorcycle and its rider lean to the same lean angle. Finally, they assume that the motorcycle tires have no width, such that the portion of the tires contacting the roadway does not change or move as the motorcycle and rider lean. This study reports physical testing that the authors conducted with motorcycles traversing curved paths to examine the net effect of these assumptions on the accuracy of the basic formulas for motorcycle lean angle. We concluded that the basic lean angle formulas consistently underestimate the lean angle of the motorcycle as it traverses a particular curved path.

The forward lighting systems on a motorcycle differ from the forward lighting systems on passenger cars, trucks, and tractor trailer. Many motorcycles, for instance, have only a single headlamp. For motorcycles that have more than one headlamp, the total width between the headlamps is still significantly less than the width of an automobile, an important component in the detection of a vehicle at night, as well as a factor in the efficacy of the beam pattern to help a driver see ahead. Single headlamp configurations are centered on the vehicle, and provide little assistance in marking the outside boundaries like a passenger car or truck headlamps can. Further, because of the dynamics of a motorcycle, the performance of the headlamp will differ around turns or corners, since the motorcycle must lean in order to negotiate a turn. As a result, the beam pattern, and hence visibility, provided by the headlamps on a motorcycle are unique for motorized vehicles.

This paper investigates the dynamics of four motorcycle crashes that occurred on or near a curve (Edwards Corner) on a section of the Mulholland Highway called “The Snake.” This section of highway is located in the Santa Monica Mountains of California. All four accidents were captured on video and they each involved a high-side fall of the motorcycle and rider. This article reports a technical description and analysis of these videos in which the motion of the motorcycles and riders is quantified. To aid in the analysis, the authors mapped Edwards Corner using both a Sokkia total station and a Faro laser scanner. This mapping data enabled analysis of the videos to determine the initial speed of the motorcycles, to identify where in the curve particular rider actions occurred, to quantify the motion of the motorcycles and riders, and to characterize the roadway radius and superelevation throughout the curve.