Cambridgeshire Police are urging passengers in cars to report drivers who use mobile phones at the wheel.
The move is part of the force’s month-long THINK! campaign.
Inspector Mark Rogers said: “When someone uses a mobile phone while driving, their reaction time becomes 50 per cent slower and they are four times more likely to have a collision, therefore, they are putting themselves and anyone else in the vehicle at great risk.
“People would not get into a car being driven by someone over the alcohol limit and yet recent research has compared using a mobile phone at the wheel with drink driving.
“Passengers should not be worried or feel awkward about challenging a driver who breaks the law: it could save a life.
Driving while using a phone is one of the ‘fatal four’ driving offences, along with speeding, not wearing a seatbelt and drink or drug driving.
Motorists are advised to turn their mobile phone off or lock it in the glove box while driving to avoid being distracted or tempted to answer.