Motorist driving while suffering from heavy cold or flu symptoms could be putting themselves in as much danger as driving after drinking alcohol.

That is the message from a practical survey of drivers carried out by insurance company Young Marmalade in conjunction with Halfords. Using black box technology to gather data on driver’s speed, braking, and cornering, the study found that colds or flu caused a major loss of concentration when behind the wheel, putting drivers, passengers and other road users at risk.

In particular reactions times dropped sharply and sudden braking became much more frequent, as motorist became less aware of surrounding traffic. The study says in the worst cases, driving ability dropped by more than 50%, or something on a par with drinking four large short alcoholic measures and then getting behind the wheel.