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The Highways Agency, tasked with looking after England's motorways, buys data on Brits' whereabouts from mobile phone networks.

The information, harvested by tracking the location of everyone's handsets and anonymising it into blocks of statistics, is used to establish which roads are used the most and when - much to the annoyance of the Telegraph this morning.

The agency is responsible for maintaining and improving the country's major trunk routes, and obviously likes to count the cars using them. The Telegraph, apparently reacting to a press release dated August 2012, is concerned about the privacy implications. But the broadsheet seems to have missed the fact that tracking phones is more anonymous, and a good deal cheaper, than tracking the cars themselves.

Historically, the agency uses induction loops buried under the road surface to count vehicles passing overhead, but that does not reveal where they're ultimately going.

Modern systems can read off the number plates using cameras and clever recognition software to work out where vehicles join and leave the network. This is important stuff when considering how to relieve congestion, provided the cameras get a good shot of the highway, which isn't always the case.

But reading number plates has huge implications for privacy, as the rozzers of Royston discovered when they illegally slurped plate numbers. Number plates relate to specific vehicles and people, allowing the owners to be individually tracked by officials, which is an unnecessary intrusion into drivers' privacy.

Mobile phone data, on the other hand, is cleansed of identifying data before delivery to the customer. Vodafone has been supplying such information to TomTom for years, and while it's not as accurate as Google's GPS-based tracking, it is comprehensive and very anonymous. The mobe networks compress the data into blocks of statistics, as explained here by El Reg in May.

That's not to say careful analysis couldn't identify an individual, particularly if they lived close enough to the monitored route to show a home location, but it's much harder to exploit than the number-plate systems being used today.

Today, tracking phones riled the Telegraph enough to gather quotes from Big Brother Watch, and claim that "the Highways Agency initiative comes just weeks after it emerged a company was using recycling bins to track the smartphones of passers-by in the City of London" - or a year before that initiative, depending on how you read the passage of time.

European mobile operators are required to store the location of every mobile handset for at least two years, for law enforcement purposes, and have been busy developing ways to make money out of that silo of information. To see it in action take a look at the map created by Malte Spitz from his location data, and consider how your own history might look.

It is important we keep an eye on how the network operators and the police use that data, but the Highways Agency has got to be one of the most benign applications around. ®

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