We accept certain risks for the benefits of modern society. We pump explosive gas into homes, we run wires with potentially fatal electrical currents through our neighborhoods, and we ski at breakneck speeds down mountains for fun.

We also allow people to operate vehicles weighing thousands of pounds at speeds that are potentially deadly if a mishap occurs. In 2011 there were 32,367 motor vehicle deaths in the US (10.4 per 100,000 population). Interestingly, this is down quite a bit from previous years. As a percentage of population the highest motor vehicle death year was 1935, with 34,494 deaths, or 27.1 per 100,000. The highest absolute number of motor vehicle deaths was in 1970, at 52,627.

The number of deaths has been mostly trending down since 1996, which is interesting because over this same period of time cell phone use has risen tremendously. There are various reasons for the decreased in fatalities – helmet laws, seatbelt laws, cracking down on drunk driving, increased car safety, and intermediate drivers licenses for new drivers to name a few. These trends have probably obscured any increase in car accidents from using portable communication devices while driving.

Recent laws have addressed this risk by requiring device users to use only hands-free devices. However, the evidence clearly shows that hands-free device use (talking or texting) is just as dangerous as using a hand-held device.

The problem is not that your hands are occupied, but that your mind is occupied. While talking on a cell phone you are distracted from scanning the road and will have slower reactions to unexpected obstacles. Information processing is the limiting factor.

A recent University of Utah study examined drivers with various levels of distraction. They found:

– Tasks such as listening to the radio ranked as a category “1” level of distraction or a minimal risk.

– Talking on a cell-phone, both handheld and hands-free, resulted in a “2” or a moderate risk.

– Listening and responding to in-vehicle, voice-activated email features increased mental workload and distraction levels of the drivers to a “3” rating or one of extensive risk.

Contributing to this problem is the illusion of multitasking – people believe they can do more than one mental task at the same time, but we can’t. We simply switch back and forth between tasks, further using mental resources to manage this switching. This results in what psychologists call interference -a decrease in performance in any task when distracted by extraneous information or performance of a simultaneous task.

Younger drivers are particularly cavalier about multitasking while driving – something that can be addressed with driver education.  This is important because younger drivers are also less experienced and are already a higher accident risk.

The implications of existing research are clear – to minimize accident risk, do not use mobile devices while driving. Do not be lulled into a false sense of safety by hands-free devices. Minimize distractions while driving – it really does take your full attention, even if it doesn’t feel like it.

Hopefully, technology will get us out of this problem it has gotten us into. Computer-assisted driving technology is advancing rapidly. Google’s driverless car (a bit of a misnomer, as there is always a driver behind the wheel) is now able to drive on city roads, and can go miles between driver interventions. Computers have one extreme advantage over humans – they are not distracted, they do not get tired or lose their attention.

Computer-assisted driving seems like the perfect solution. It will be years before such technology becomes standard, however, so in the meantime – don’t text and drive.


Posted by Steven Novella

Founder and currently Executive Editor of Science-Based Medicine Steven Novella, MD is an academic clinical neurologist at the Yale University School of Medicine. He is also the host and producer of the popular weekly science podcast, The Skeptics’ Guide to the Universe, and the author of the NeuroLogicaBlog, a daily blog that covers news and issues in neuroscience, but also general science, scientific skepticism, philosophy of science, critical thinking, and the intersection of science with the media and society. Dr. Novella also has produced two courses with The Great Courses, and published a book on critical thinking - also called The Skeptics Guide to the Universe.