Severe Obesity as a form of Impaired Driving?

NOTE: This article is part of a series investigating the definition of “impaired driving” as it occurs in society, traffic safety and driver safety professional networks.

A recent study searched for links between a driver’s Body Mass Index (BMI – a key measure to determine clinical obesity in people) and their crash rate.  The findings were preliminarily published in “ScienceNOW” (Link) on October 26th of this year.

The study focused on commercial drivers who typically deal with long hours, a sedentary lifestyle punctuated with brief intervals of physical activity and a lot of stressful situations over scheduling and traffic.  Also linked to these drivers are very irregular sleep patterns and typically a deficient amount of quality sleep.

Due to the amount of miles driven, commercial operators are predisposed to crashes and many of these are already linked to fatigue, drowsiness and medical issues.

Two years ago, the research team focused on driver height and weight as factors in crash occurrence.  The height and weight can be used to derive BMI:  BMI greater than 25 is considered “overweight”; greater than 30 is considered “obese”; and greater than 35 has been labeled “severely obese” by the study.

During their first 2 years on the road, drivers in the study group with a BMI higher than 35 (“severely obese”) were 43% to 55% more likely to crash than were drivers with a normal BMI, the team reports in the November issue of Accident Analysis & Prevention (Link).

The specific causal reasons have not been clearly documented and speculation is focused on obstructive sleep apnea (OSA), limited agility and fatigue associated with other medical factors other than OSA.

There are a range of medical issues that can cause a driver to become disqualified as a “Commercial Motor Vehicle Operator” under the Federal Motor Carrier Safety Regulations (FMCSRs).   Presently, a person with severe obesity might be at elevated risk of developing some of the conditions that could lead to disqualification, but the simple weight or BMI of a person has no direct connection to qualification as expressed in Part 391.41. 

Additionally, the link between crashes and supposed causes (in this case BMI over 35) does not constitute grounds for disqualification; however, it may be a warning sign that drivers, their employers, health providers and EAP program administrators should be working in concert to manage a BMI greater than 35 downward to a lower number where feasible (if not for crash reductions, then for the many well documented health benefits of maintaining a lower BMI). 

Driving a commercial vehicle for a living presents special challenges, but comes with added responsibilities, too.  It’s a difficult challenge for many drivers to get the help and relief they need to make consistent lifestyle changes.  If they could, they’d benefit directly and if the study mentioned above is representative of all drivers, then we’d see potentially lower crash rates, too.

Stay tuned for more articles examining the issue of “impaired driving” in its many forms.

SafetyFirst provides a range of driver safety programs to more than 3,800 active fleet clients and through a network of more than 75 insurance providers. 

Our programs range from MVRs to hotline reports — all designed to identify specific drivers with specific habits that should be “brought to the front of the line” to get help from their supervisors immediately.  This compassionate intervention in a timely fashion has been documented to reduce crash rates by 20 to 30% without expensive telematics devices that cost 100 times more per vehicle per month than our proprietary program.

However, we also embrace technology and have helped our clients better leverage their telematics investments.  In one case, we worked with a client to design and implement an enhanced coaching program that reduced the actual behavior that triggers telematic speed alertsThey dropped the alerts by 600% in the first year.


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