A weblog by Will Fitzgerald

Driving while using a cell phone

There are two questions: Is driving while talking on a cell phone safe? and Is it as dangerous as driving while drunk?

After reviewing some earlier studies, and looking at a new Virginia Tech study, I’d say the answer is a definite yes to the first question; and a probably not to the second question (not as dangerous as driving drunk, but maybe “only” 1/4 as dangerous.)

Details follow. All of the papers below are available online, and discuss (for the most part) their methodologies and metrics. I used to look at this pretty carefully when I worked for a startup company that hoped to put voiced-activated controls in cars.

Is driving while talking on a cell phone safe?

The National Highway Traffic Safety Administration (NHTSA) answers the question “Does cell phone use while driving cause traffic crashes?” by stating:

Research shows that driving while using a cell phone can pose a serious cognitive distraction and degrade driver performance. The data are insufficient to quantify crashes caused by cell phone use specifically, but NHTSA estimates that driver distraction from all sources contributes to 25 percent of all police-reported traffic crashes.

A epidemiological study (Redelmeier and Tibshirani 1997) indicated a quadrupling of a risk of collision, having tracked 669 drivers and their calling habits.

Strayer and Drew 2004, in a driver simulation task, showed decreased reaction times, increased following distance and slower recovery times. They compared younger and older drivers and noted:

Interestingly, the net effect of having younger drivers converse on a cell phone was to make their average reactions equivalent to those of older drivers who were not using a cell phone.

The most recent large scale study I found, by Virginia Tech Transportation Institute this year engaged in several “large-scale, naturalistic driver studies” which looks impressive methodologically. They reports

In VTTI’s studies that included light vehicle drivers and truck drivers, manual manipulation of phones such as dialing and texting of the cell phone lead to a substantial increase in the risk of being involved in a safety‐critical event (e.g., crash or near crash). However, talking or listening increased risk much less for light vehicles and not at all for trucks. Text messaging on a cell phone was associated with the highest risk of all cell phone related tasks.

Is driving while talking on a cell phone about as dangerous as driving while drunk?

Strayer, Drews and Crouch 2003 used a “high-fidelity driving simulator” to compare driving while using a cell phone and driving while drunk, measuring six performance variables (brake onset time, braking force, speed, following distance, recovery time). They conclude “when controlling for driving difficulty and time on task, cell-phone drivers may actually exhibit greater impairments (i.e., more accidents and less responsive driving behavior) than legally intoxicated drivers.”

The same Virginia Tech Transportation Institute 2009 Study reports “For example, talking and listening to a cell phone is not nearly as risky as driving while drunk at the legal limit of alcohol.”


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