Having a bite to eat or a drink while driving almost doubles the risk of crashing, a study suggests.
Braking time worsened when drivers were eating or drinking
Motorists end up driving more slowly and carefully but often cannot stop in time to avoid a crash, the research for Privilege Insurance found.
After testing 26 drivers on a car simulator, researchers suggested that the "increased workload" of eating or drinking affected driver reactions.
Police said eating and drinking while driving was definitely a distraction.
In the simulator, drivers had to drive an urban route once without eating, and once while eating from a bag of sweets or drinking from a bottle of water at two intervals, just as a pedestrian stepped onto the road.
The number of crashes doubled during the food and drink trial.
Nine out of 10 happened when the driver was eating or drinking, resulting in a collision with a pedestrian.
"The results strongly indicate that eating or drinking while driving increases the risk of a crash," said Mark Young, a researcher from Brunel University, London, who carried out the study.
"Drivers may not perceive the risk to be any higher than other menial in-car tasks, but the impaired reactions combined with the increased workload suggest drivers should exert caution."
Alan Jones from the Police Federation for England and Wales said safety concerns had focussed on the use of mobile phones while driving.
"But eating and drinking behind the wheel certainly is a distraction and certainly it should be enforced quite rigorously."
The 26 drivers tested were recruited from the driver participant pool maintained at Brunel University, and all drive on average of 12,000 miles a year.
Privilege Insurance's Kate Syred said: "These results are extremely worrying as they suggest that consuming food or drink while driving has a similar effect on driver workload and reaction times as using a hand held mobile phone, which is of course now banned."