High-tech mobile phone detectors will be used by police in a bid to stop motorists using handsets at the wheel.
The new technology can determine how many cars on a stretch of road have phones being used without hands-free kits.
Hampshire and Thames Valley police forces are the first to be issued with the devices.
The roadside unit can spot a phone being used and will flash a mobile phone symbol at the vehicle from a sign, to advise the driver to stop using their mobile phone.
The technology can also enable police to identify hotspots where mobile phones are frequently used by motorists.
A spokesman for the two forces said: "The technology can detect when Bluetooth is being used but cannot detect if a passenger is using the phone, but the sign will still be activated reminding motorists of the distraction of a mobile phone whilst driving."
The new device will be first used on the A34 in Oxfordshire before being used across the Thames Valley and Hampshire areas.
The campaign is being supported by Kate Goldsmith who lost her daughter Aimee Goldsmith after a lorry driver crashed into the car she was a passenger.
He was using his mobile phone to change music whilst driving.
Ms Goldsmith’s 11-year-old was killed along with her stepbrothers Josh Houghton, aged 11, Ethan Houghton, aged 13, and the brothers' mother Tracey Houghton, aged 45.
Ms Goldsmith said: "I am supporting this campaign and welcome any technology which can assist in educating people and stop them from using their mobile phones whilst driving.
"My daughter's death was completely avoidable.
"Please don't use your mobile phone whilst driving, it's not worth the risk."
RAC road safety spokesman Pete Williams said: "Driving and using a handheld phone do not mix, it is an incredibly dangerous and distracting combination.”
