The Highways Agency is tracking the movements of millions of motorists via their mobile phones and satellite navigation systems, raising concerns over privacy.
A trial by the agency involved collecting data from satnavs and mobile phones in order to examine traffic trends, in addition to real-time data that is used to provide assistance to traffic management in order to let motorists avoid congestion and accidents.
Roads being used to conduct the trial include the M25, M11, M4, A3 and A20, all in the south-east, with mobile phone companies' data about users geo-location also being used as part of the trial, as opposed the traditional method of number plate recognition via cameras in overhead gantries.
But the mobile data trial has attracted criticism from privacy campaigners who are concerned about people being unaware about how their data is being collected and used.
"This is yet another example of how our lives are being monitored at an extremely detailed level, and just how much of that data is being shared and sold on for a vast range of purposes," said Nick Pickles, director of privacy campaign group Big Brother Watch.
"People will probably have no idea that this information is being used by the Highways Agency," he continued.
He added: "The question has to be asked if there is a less intrusive way to get this kind of data, and if it is so essential that it is so detailed as to require live data from the devices in people's cars."
The Highways Agency has responded to the criticisms by stating that all the data it collects is done so anonymously and that individuals and their movements can't be identified.