A US senator is floating the idea of using digital car numberplates, which would switch to advertisements when vehicles are stuck in traffic, as a way to raise money to tackle a massive budget deficit.

The electronic plates would look like standard plates while in motion but when a car has stopped for more than four seconds scrolling advertisements would be displayed to people sitting in the vehicles behind.

Advertisers would buy space from California’s Department of Motor Vehicles.

Additional features of the technology include the ability for the plates to be used to display public service announcements such as, emergencies, missing children alerts or traffic information.

Drivers would also be able to have their plates show personal messages, such as the name of their favourite sports team.

According to London’s Telegraph, the state currently is looking into a number of ideas to reduce its $US19 billion ($21.6 billion) debt.