observably angry, sad, crying, and/or emotionally agitated increases
the risk of a crash by 9.8 times compared with model driving.
Several driver performance errors, including committing a
right-of-way error, sudden or improper braking or stopping, and
being unfamiliar with a vehicle or roadway, had the highest risks
of any contributing factors analyzed for this study. The risk estimates for these errors were hundreds of times higher than
Driver judgment errors (e.g., speeding well
above the speed limit or traveling too fast for conditions) and
other aggressive driving behaviors increase crash risk 11.1 times
more than model driving.
Interacting with in-vehicle devices
that do not include the more standard radio or HVAC tasks, such
as using a touchscreen interface, had a high odds ratio (i.e., 4.6
times higher than model driving) and a fairly high baseline prevalence (0.83% of trips).
Several factors previously thought to
constitute significant driver risk factors, such as particular distractions (e.g., applying makeup) or errors (e.g., following too closely),
were found to be much lower in prevalence in this analysis. Other
factors posed much lower risks than previously thought, or even had
a protective effect (e.g., interacting with children in the rear seat)
Drivers are engaging in distracting activities more than 50% of the
time while they are driving, resulting in a crash risk that is 2.0
times higher than model driving. Interacting with a
handheld cell phone occurs more than 6% of the time, with a risk
that is 3.6 times higher than model driving.
In addition, cell
phone activities have changed even in recent years with the
emergence of texting and browsing online. This is probably the
single factor that has created the greatest increase in US crashes in