Next time you're about to head somewhere in your car but you're not feeling entirely great, emotionally speaking, you might want to consider postponing your trip.

Researchers in the US have compiled what they say is the largest crash-based driving study ever conducted, and the data shows that drivers who are observably angry, sad, crying, or emotionally agitated increase their crash risk nearly tenfold when they get behind the wheel.

What's more, drivers who engage in distracting activities that make them take their eyes off the road – including using mobile phones or using touchscreen menus on in-car instrument panes – more than double their crash risk. Even scarier, more than half of us on the roads actually engage in this kind of distracted driving, according to the study.

"These findings are important because we see a younger population of drivers, particularly teens, who are more prone to engaging in distracting activities while driving," said Tom Dingus, director of the Transportation Institute at Virginia Tech. "Our analysis shows that, if we take no steps in the near future to limit the number of distracting activities in a vehicle, those who represent the next generation of drivers will only continue to be at greater risk of a crash."

To create their crash database, the researchers collected data from more than 3,500 participants across the US over a 3-year period, tallying up over 1,600 verified 'crash events'. These ranged in severity from low, including tyre and curb strikes, to severe, such as crashes that had to be reported to the police.

Of the total crash count represented in the data, 905 of the incidents were high severity crashes involving injury or property damage. And nearly 90 percent of these crash events included driver-related factors, such as fatigue, impairment, or distraction.

"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 Dingus.

While the study encompasses some obvious risk factors – for example, driving above the speed limit increases the likelihood of crashing by about 13 times – other factors surprised the researchers. Applying makeup while behind the wheel, and travelling too closely behind other vehicles, both of which you might assume could be dangerous, didn't factor in the crash data.

Reaching for an item increases the risk of a crash by nine times, although reaching for a phone is only six times. Dialling a number on the phone once you've got it in your hand, however, is very perilous – making a crash 12 times more likely.

"All of these findings are especially important as we work with policymakers, educators, drivers themselves, law enforcement officials, and vehicle designers to define and help mitigate driver risks," said Dingus. "Our ultimate goal is to identify those risks and to help others create the necessary countermeasures to ensure the safety of ground transportation users."

The findings are reported in Proceedings of the National Academy of Sciences.