Has Increased Body Weight Made Driving Safer?

Abstract

We develop a model of alcohol consumption that incorporates the negative biological relationship between body mass and inebriation conditional on total alcohol consumption. Our model predicts that the elasticity of inebriation with respect to weight is equal to the own-price elasticity of alcohol, consistent with body mass increasing the effective price of inebriation. Given that alcohol is generally considered price inelastic, this result implies that as individuals gain weight, they consume more alcohol but become less inebriated. We test this prediction and find that driver blood alcohol content (BAC) is negatively associated with driver weight. In fatal accidents with driver BAC above 0.10, the driver was 7.8 percentage points less likely to be obese than drivers in fatal accidents that did not involve alcohol. This relationship is not explained by driver attributes (age and sex), driver behaviors (speed and seatbelt use), vehicle attributes (weight class, model year, and number of occupants), or accident context (county of accident, time of day, and day of week).

Obesity and motor vehicle deaths: a panel-data analysis

“…Recent research on the relationship between obesity and motor vehicle fatalities has focused on the determinants of death or serious injury to drivers given the event of a motor vehicle crash. The consensus from this research is that obesity is associated with a greater risk of fatality in the event of a motor vehicle crash (see, in particular, Carter et al (2014), Desapriya et al (2014), Dunn and Tefft (2014), Jehle et al (2012), Joseph et al (2017 and Rice and Zhu (2013)). Although earlier research indicated that heavier drivers and passengers might be less at risk of dying once a crash has occurred because of the so-called cushion effect associated with the distribution of subcutaneous fat, more recent analyses have found little evidence in support of that hypothesis (Dunn and Tefft, 2014).…”

“…The consensus from this research is that obesity is associated with a greater risk of fatality in the event of a motor vehicle crash (see, in particular, Carter et al (2014), Desapriya et al (2014), Dunn and Tefft (2014), Jehle et al (2012), Joseph et al (2017 and Rice and Zhu (2013)). Although earlier research indicated that heavier drivers and passengers might be less at risk of dying once a crash has occurred because of the so-called cushion effect associated with the distribution of subcutaneous fat, more recent analyses have found little evidence in support of that hypothesis (Dunn and Tefft, 2014). The suggestion of a U-shaped pattern (lower BMI and very high BMI are associated with a greater risk of fatality) has been reported by a number of studies, and others find no statistical relationship between death rates or fatality risk and being overweight (as determined separately from obese) (Jehle, 2012;Zhu et al, 2006Zhu et al, , 2010Simmons and Zlatoper, 2010;Sivak et al, 2010).…”

“…Because seat belts are designed for the average driver who is assumed to have a BMI of 25 (Joseph et al, 2017), most restraint systems offer a poor fit for those who are overweight or obese. As a result, seat belts may be less effective when deployed, and obese drivers may be less likely to wear them (Dunn and Tefft, 2014;Reed et al, 2011;Zhu et al, 2010). Further, there is significant evidence of emergency and post-operative complications among obese individuals, including the higher risk of respiratory failure or pneumonia (Desapriya et al, 2014;Joseph et al, 2017).…”