Select Risk Factors Associated with Causes of Motorcycle Crashes

​​Motorcyclists—motorcycle riders and their passengers—have the highest risk of fatal injury among all motor vehicle users. In 2016, 5,286 motorcyclists died in traffic crashes in the United States (NCSA 2018). Per mile traveled, motorcyclist fatalities occurred nearly 28 times more frequently than passenger vehicle occupant fatalities in traffic crashes (NCSA 2018). Like accidents across all modes of transportation, motorcycle crashes are complex events that can be influenced by multiple human, vehicle, and environmental factors. However, because motorcycles afford riders less protection, the likelihood of injuries and fatalities in a crash is much greater. In this safety report, the National Transportation Safety Board (NTSB) assesses select risk factors associated with the causes of motorcycle crashes in the United States and makes recommendations for improving motorcycle crash prevention.

The Federal Highway Administration (FHWA) provided the data analyzed in this report from its 2016 Motorcycle Crash Causation Study (MCCS). The MCCS represents the most recent data available for studying motorcycle crashes and risk factors in the United States since the US Department of Transportation published its comprehensive Motorcycle Accident Cause Factors and Identification of Countermeasures report in 1981. The NTSB analyzed the MCCS crashes involving a motorcycle with an engine displacement that exceeded 50 cubic centimeters or a maximum design speed above 31 mph, and at least one reported injury sustained by the motorcycle rider or passenger. All crashes occurred in Orange County, California, between 2011 and 2015. The NTSB’s research goals were to

1. ​​ identify and assess factors that contribute to motorcycle crash risk,
2. compare these factors with previous research findings about motorcycle crash risk, and
3. evaluate the need for motorcycle safety improvements.

This safety report analyzed select risk factors associated with the causes of motorcycle crashes and evaluated strategies for crash prevention. The MCCS data were appropriate for identifying factors associated with an increase or decrease in motorcycle crash risk that warranted further evaluation. These factors were then examined as potential safety issue areas and compared to existing motorcycle safety research and publications to determine the need for safety improvements.

Previous NTSB safety recommendations to encourage universal motorcycle helmet use and to establish a per se blood alcohol concentration (BAC) limit of 0.05 grams per deciliter or lower for all drivers were not reiterated in this report. Nearly 100% of all motorcycle riders and passengers analyzed in the MCCS were wearing helmets, presumably a direct result of the universal helmet law in California. Although the use of a helmet is an important safety issue associated with the protection of motorcycle riders, injury mitigation (and therefore helmet use) was beyond this safety report’s scope and stated focus on motorcycle crash causation and crash prevention. Concerning the role of alcohol, the BAC for the majority of the riders and passengers was either not tested or not available in the MCCS.

The NTSB identified the following motorcycle safety issues:

• Inadequate integration of motorcycles in crash warning and prevention systems and with vehicle-to-vehicle and vehicle-to-infrastructure systems. Multiple-vehicle crashes involving a motorcycle and another motor vehicle represented the majority of the crashes in the MCCS. In many of these crashes, the other vehicle driver reported not detecting the motorcycle or that a dangerous condition existed, and the motorcycle rider reported having insufficient time to react and complete a collision avoidance maneuver. Vehicle-based crash warning and prevention systems on passenger vehicles and connected technologies (vehicle-to-vehicle and vehicle-to-infrastructure) all have the potential to prevent crashes involving motorcycles by improving motorcycle conspicuity. However, these systems are not always being designed to detect or fully integrate motorcycles.
• Need for enhanced braking and stability control systems on motorcycles. The reduced stability on a motorcycle compared to four-wheeled vehicles can make braking, swerving, and other collision avoidance maneuvers more complicated. More than a third of the crashes analyzed involved a loss of control that contributed to crash causation. Running wide on curves and slide outs due to inappropriate braking were among the most common loss-of-control scenarios. More widespread availability of enhanced braking and stability control systems on motorcycles could improve safety by enhancing the effectiveness of braking, collision avoidance performance, and stability control for both novice and experienced riders.
• Limitations of the most recent data collected on motorcyclist alcohol and other drug use and motorcycle crashes in the United States. Although alcohol and other drug use is well established as a risk factor in motor vehicle collisions, more focused research is needed to understand the contribution of alcohol and other drug use as a risk factor in motorcycle crashes and whether specific countermeasures could reduce alcohol- and other drug-related motorcycle crashes. The MCCS attempted to collect the data needed to support such research; however, rider BAC and any indicator of the presence of drugs other than alcohol were either not tested or not available in many cases.
• Need to evaluate the effectiveness of motorcycle rider licensing procedures. Licensing procedures are intended to reduce crashes, injuries, and fatalities by requiring that riders have the basic knowledge and skills to ride a motorcycle safely. However, there is widespread variation in motorcycle rider licensing procedures across the United States. Despite efforts to ensure that all riders are licensed, the greater number of unlicensed riders involved in fatal crashes, when compared to unlicensed drivers of other motor vehicle types, has remained largely unchanged over the past decade. There has been limited independent research on unlicensed riders or the effectiveness of motorcycle rider licensing procedures, which makes it difficult to measure the impact these procedures are having on reducing motorcycle crashes, injuries, and fatalities.

As a result of this safety report, the NTSB makes recommendations to the National Highway Traffic Safety Administration, the FHWA, the Motorcycle Industry Council, the American Motorcyclist Association, and the Motorcycle Safety Foundation.