US: Helmets, roadway conditions and weather: what makes an impact on motorcycle fatalities

Most research studies have led to the conclusion that wearing helmets does make a difference in decreasing fatalities and head injuries for motorcycle riders. Some have pointed out that other factors such as population density, weather (temperature and precipitation), rider chracteristics (age, risk perception), and crash characteristics such as speed and the influence of alcohol, also play an important role in influencing helmet wearing and, in turn, motorcycle fatalities and injuries.

To learn more about the possible influence of these non-helmet factors and how they may impact on motorcycle helmet wearing, Konstantina Gkritza examined data from six observational surveys of motorcycle riders and passengers from Iowa, USA. Iowa, along with Illinois and New Hampshire, is one of the three states that do not require motoryclists to wear helmets. In the ten-year period, 1995-2005, the motorcycle fatality rate increased by an average of 46%, while other motor vehicle fatalities during this period declined by 15%. About 27% of the fatally injured motorcyclists were wearing a motorcycle helmet.

Iowa’s motocycle observational surveys were conducted annually between 2000 and 2006. About 90 000 observations were made, and data were collected on roadway conditions as well as weather and helmet wearing. Gkritza used multivariate statistical methods to examine all of the observations and measure how much of an influence helmet wearing, roadway conditions, and weather had on fatalities.

There were few findings of significance in Gkritza’s statistical analyses. The one exception was that there was an association between helmet wearing and the passenger and the operator – when a passenger wore a helmet, the operator was also more likely to wear one as well. This may be an important factor in promoting helmet use and education campaigns.

Gkritza K. Modeling motorcycle helmet use in Iowa: Evidence from six roadside observational surveys Accident Analysis and Prevention 2009;41(4):479–484.

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