Studying motorcycle crashes is expected to yield better counter measures.
Accidental deaths of motorcyclists have been rising recently and one way to combat that is to conduct a study of crash causes, with an eye toward what might be done to reduce those numbers.
Statistical analysis has suggested that studying 700 to 750 motorcycle crashes will provide valid data on which to base effective counter measures. Dr. Samir Ahmed, the head researcher for the study in question, offers here some of the thinking behind that conclusion.
The analysis is key to the success of the study because previously, motorcycle industry groups had decided to withhold money they raised for the study because they did not believe the study would produce valid results with fewer than 900 crashes studied.
There are 28 questions that the study will seek to answer, said Dr. Samir, having to do with a variety of factors that lead to crashes. They include:
5 - human factor
4 - environment (roadway, traffic)
5 - motorcycle and vehicle
4 - speed
1 - trip-related (destination, origin)
5 - conspicuity (visibility, awareness of other drivers)
1 - rider training
2 - protective equipment
1 - crash type and configuration
In their analysis, Dr. Samir's group examined each of these areas to determine the Statistical Power and the Significance Level that differing numbers of crashes studied would produce. Statistical Power is the probability of the data leading to rejection of an untrue hypothesis. Common practice is to work for no less than an 80 percent Statistical Power. Significance Level is the likelihood of rejecting a true hypothesis. Statisticians want the Significance Level to be no higher than 5 percent.
The analysis then compared these factors for this study in each of these areas with the same factors in the two commonly cited previous motorcycle crash studies, the Hurt Report and MAIDS. The 900 crash figure cited previously is based in part on the fact that both these two studies considered approximately that number of crashes. Dr. Samir noted that he received an email from Dr. Harry Hurt, the head of the study named after him, about a month before he died stating that the 900 figure their study used had no unique significance. Nor was the MAIDS study of 921 crashes based on any analysis, it was just the number they had available for study.
What the analysis showed, said Dr. Samir, is that for the majority of the key factors, it will not be necessary to study 900 crashes in order to get information that is valid and compares well to data from the Hurt and MAIDS studies.
For example, to achieve results comparable to MAIDS in regard to rider training, only 561 crashes would need to be studied, and only 166 crashes would meet the level in the Hurt Report.
At the same time, at least one factor would require far more crashes to be studied. Because there is such a variation in motorcycle engine sizes, a really good study in that area would require 1,856 crashes. The MAIDS researchers themselves only considered 921 crashes, so even their data fails to meet the Statistical Power and Significance Level targets.
"We need to focus on those factors that can be influenced by counter measures," said Dr. Samir, and engine size is not necessarily one of those.
The results of Dr. Samir's statistical analysis were presented to the working group of organizations involved in this study, including the Motorcycle Safety Foundation (MSF), which is holding $2.8 million to be used if the study is deemed adequate. The MSF has not made any announcements regarding any change in their previous stance.
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Comments
Thanks for the update on how they plan to use the sample size of 700-750 accidents to get statistically accurate data analysis.
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