Driving while sad is far more likely to result in a crash than being tired or using a cell phone, a new study has shown.Many road signs warn motorists to pull over if they are feeling tired, but new research suggests that a healthy emotional state is far more important for safe driving.Feeling sad, angry or agitated behind the wheel raises the risk of an accident by nearly 10 times. In contrast, fatigue makes a crash three times more likely, while talking on a cellphone only doubles the risk.In fact talking on a cellphone was found to be no more distracting for motorists than fiddling with the radio or air conditioning, US researchers at Virginia Tech found. And interacting with a youngster while driving actually lowers the chance of a smash. Likewise, applying make-up or eating food do not cause significant problems."We have known for years that driver-related factors exist in a high percentage of crashes, but this is the first time we have determined the extent of it," said Tom Dingus, the lead author."Driving while angry, sad, crying or emotionally agitated increases risk of a crash by 9.8 times compared with model driving.The biggest risk factor was consuming drink or drugs behind the wheel - raising the chances of a crash more than 35 times.Researchers used in-car video cameras to monitor habits of more than 3500 drivers across the US. ..