They can also set up licence plate accounts or receive bills in the post.

BBC: Golden Gate: Electronic tolls for San Francisco bridge

It has also asked the Highways Agency to look at whether new licence plate recognition technology could allow free-flow charging.

BBC: Dartford charge suspension considered at busy times

Under the new rules, which came into effect last year, a licence plate belongs to the car even if the owner changes address.

ECONOMIST: French number plates

But for whom does a licence plate speak?

ECONOMIST: The latest battle over licence plates

The plan involves an extensive network of cameras, licence-plate readers and weapon-detectors.

ECONOMIST: Terrorism

The initiative, which dates back to 2005, involves an extensive network of security cameras, licence-plate readers and weapon-detectors which work together to spot threats and deter terrorist surveillance.

ECONOMIST: New York expands its counterterrorism monitoring system

Blacks jotted down licence-plate numbers on scraps of paper.

ECONOMIST: The Ku Klux Klan

In April British members of Parliament learned that almost a year earlier the home secretary, Jacqui Smith, had secretly authorised the transfer of licence-plate data recorded by roadside cameras to foreign intelligence agencies.

ECONOMIST: Data mining