Evaluating the combined effect of alcohol-involved and un-helmeted riding on motorcyclist fatalities in Taiwan

Background: Alcohol-involved riders tend to engage in other risk-taking behaviours such as un-helmeted riding
which could further increases injury severity. The combined effect of alcohol-involved and un-helmeted riding
on fatal injuries is rarely investigated. This study investigated the interaction effect between blood alcohol
concentration and helmet use on fatal injuries.
Methods: This study used the National Taiwan Traffic Crash Dataset for the period from 2011 to 2015. Data on
road crashes involving a motorcycle and an automobile were extracted and analysed. Multiple logistic regression
models were used to calculate the adjusted odds ratio (AOR). We calculated an interaction effect for blood
alcohol concentration and helmet use based on STROBE guidelines.
Results: There were a total of 669,292 motorcyclist casualties; among these casualties, 3459 (0.5 %) motorcyclists
sustained fatal injuries. Alcohol-involved riders were 9.47 times (AOR=9.47; 95 % CI=8.75–10.25)
more likely than sober ones to sustain fatal injuries. Alcohol-involved and un-helmeted riders were approximately
18 times (AOR=18.1; CI: 15.9–20.4) more likely to sustain fatal injuries than sober and helmeted riders.
Riders involved in head-on crashes and approach-turn motorcycle crashes had an increased probability of sustaining
fatal injuries by 240 % (AOR=3.4; 95 % CI=2.91–4.09) and 132 % (AOR=2.3; 95 %
CI=2.016–2.67), respectively.
Conclusions: This study found that alcohol-involved riding acts synergistically with un-helmeted riding to increase
motorcyclist injury severity.