People + Process = Performance

Two Troubling Studies on the Effect of Obesity and Driving: Part 2

In this part two of my blog series on obesity and driving.  In Part 1 of this blog series I discussed a study (1) that examined normal weight and obese truck drivers based on BMI.  The study showed that severely obese drivers were 43% to 55% more likely to crash than were drivers with a normal BMI.  This is a striking correlation between weight and driving accidents.  Reading this study caused me to do a little more research on obesity and driving which is how I came across this second study:  Driver obesity and the risk of fatal injury during traffic collisions (2).

This study looked at how obesity affects injury outcomes among vehicle occupants involved in traffic collisions.  The goal was to determine if there was an association between obesity level with the risk of death among drivers of passenger vehicles.  They also wanted to look at if the risk could be modified by driver sex, seat belt use and collision type.

They were able to determined estimated risk ratios (RRs) for drivers with different BMI.  The results were the following:  RRs were slightly raised for underweight drivers (RR=1.19, 95% CI 0.86 to 1.63). RR increased with higher BMI categories and were 1.21 (0.98 to 1.49) for BMI 30–34.9, 1.51 (1.10 to 2.08) for BMI 35–39.9 and 1.80 (1.15 to 2.84) for BMI ≥40. Estimated BMI effects did vary gender, however, the authors found no meaningful variation across levels of vehicle type, collision type or seat belt use.

The authors concluded that obese vehicle drivers are more likely to die from traffic collision-related injuries than non-obese occupants involved in the same collision.

While at first glance there may not be an obvious connection between the two studies because one look at commercial truck drivers and crashes while the other looked at passenger vehicles and risk of death the common denominator is the significant effect that obesity has on individuals.  Employers that have fleets need to be aware of the increased risk of accidents with severely obese employees as well as the increased risk potential of death for their obese employees if they should be involved in an accident.  Vehicle makers need to take this information into consideration when designing the cab and driver’s seat to ensure it protects and fits all weight ranges as much as possible.  Individuals need to be aware of these studies as knowing the results may motivate them to make lifestyle changes to lower their weight.


  1. Obesity is associated with the future risk of heavy truck crashes among newly recruited commercial drivers
  2. Driver obesity and the risk of fatal injury during traffic collisions