Carried out by the Virginia Tech Transportation Institute in the US and reported in the Proceedings of the National Academy of Sciences, the study found that drivers also more than double their crash risk when they engage in distracting activities, such as using a handheld cell phone, reading or writing, or using touchscreen menus on a vehicle instrument pane.

The institute’s research also found that drivers engage in some type of distracting activity more than 50% of the time they are driving.

The researchers used results from the Second Strategic Highway Research Program Naturalistic Driving Study, the largest light-vehicle naturalistic driving study ever conducted with more than 3,500 participants across six data collection sites in the United States.. The results are said to provide the most conclusive findings to date of the biggest risks faced by drivers today.

The research found that driver-related factors that include fatigue, error, impairment, and distraction were present in nearly 90% of the crashes.

“We have known for years that driver-related factors exist in a high percentage of crashes, but this is the first time we have been able to definitively determine — using high-severity, crash-only events that total more than 900–the extent to which such factors do contribute to crashes,” said Tom Dingus, lead author of the study and director of the Virginia Tech Transportation Institute.

Travelling well above the speed limit creates about 13 times the risk, and driver performance errors such as sudden or improper braking or being unfamiliar with a vehicle or roadway have an impact on individual risk.

Yet factors previously thought to increase driver risk, such as applying makeup or following a vehicle too closely, were only minimally present or were not present at all in the crashes analysed.