Motorcycle safety advocate Dan Petterson of SMARTER delves into what’s really behind the registration and injury statistics
Today is part three of a guest post by my friend Dan Petterson, president of motorcycle safety group SMARTER. Dan is a leading voice in Michigan for increasing motorcycle safety for all enthusiasts and owners. He and I met during the motorcycle helmet law repeal, of which we were both outspoken critics. Dan says we need to start by truly understanding what is behind the motorcycle accident death and injury statistics – for this is the key to formulating and improving greater safety interventions.
Last week, Dan discussed Michigan motorcycle accident statistics. Today he’s covering fatalities per registered motorcycles and why we can’t assume one fatality goes for one registered motorcycle:
“The standard (historical) way to calculate fatality rate is to compare the number of deaths to the number of registered motorcycles. The rate is typically fatalities per 100,000 registered motorcycles. For example, if there are 275,000 registered motorcycles in a given year and in that same year 120 individuals are killed in motorcycle crashes, then the fatality rate per 100,000 registered motorcycles is 43.64
To calculate the fatality rate per 100,000 registered motorcycles, first divide the total registrations by 100,000 (275,000 ∙/∙ 100,000 =2.75). Second divide the number of fatalities (120) by 2.75= 43.6 fatality rate (fatalities per 100,000 registered motorcycles.
We have calculated fatality rates this way for years assuming, incorrectly, there is one motorcyclist per motorcycle.
Also, it is difficult to put much trust in comparing fatalities per 100,000 registered motorcycles between states, because states do not count registrations in the same way. Some states include scooters, mopeds and/or ATV, and some do not.
Even within a single state, the number of motorcycle registrations is a moving target. In a state like Michigan with a short summer riding period, the number of registrations may be at a low in the months of December, January or February and begin to rise in March and April as good weather arrives. This is especially the case if the spring weather is warm and dry. So while the end of the year number of fatalities is a firm number, the registration number can vary.
Even so, fatality rate per 100,000 registered motorcycles is a better measure of effectiveness than just the raw number of fatalities or injuries, because to some degree, it takes into account the popularity of motorcycling. It is a measure of the increase (or decrease) in danger, albeit a somewhat weak measure.
Michigan Motorcyclist Safety – Measuring Results, Dan Petterson, Ed.D.
Data source – fatalities: Traffic Safety Facts – Michigan, National Highway Traffic Safety Administration
Data source – registrations: Michigan Office of Highway Safety Planning
Stay tuned for next week, when we will finish the series and cover crash fatalities per vehicle miles traveled.