Scottish passengers could be the first in the world to experience autonomous buses.

The government has said that self-driving buses will be shuttling across the Forth Road Bridge in Scotland by 2021, carrying half a million passengers a year.

The Department for Business is pumping £4.35m into a £6m project that will see five single-decker buses, each carrying 42 passengers, running on a 14-mile journey.

The vehicles will link Fife with Edinburgh Park, the tram and rail interchange on the west side of the city. It offers a train journey of 10 minutes or less to Waverley station in the Scottish capital.

The bus service will operate every 20 minutes, and the weekly ridership is expected to be 10,000.

Since the Queensferry Crossing opened in 2017, the 1964 Forth Road Bridge has been mainly restricted to buses and taxis.

Bus drivers need not start looking for alternative employment; to comply with safety legislation, each vehicle will have a driver on board.

Driverless trains have been operating on the Docklands Light Railway in east London since 1987. But there is a huge difference between trains running on tracks on a closed system and buses driving on the open road.

Autonomous vehicles are fitted with sensors to detect other road users, with the control system responding by changing speed and direction.

Plans are also under way for a private hire pilot scheme in the London borough of Greenwich, where Addison Lee will deploy a fleet of 15 self-driving Land Rover Discovery vehicles.

Initially they will feed the Tube station at North Greenwich Station. Next, they will connect transport hubs in the borough that do not currently have a link.

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The third stage is “a restricted on-demand service”. The final aim: a “go anywhere in borough service.”

There are also plans for a project called ServCity which will offer “a premium mobility service across four Greater London boroughs,” though details are sketchy.

The business secretary, Greg Clark, said: “Autonomous vehicles and their technology will not only revolutionise how we travel, it will open up and improve transport services for those who struggle to access both private and public transport.

“Self-driving cars will revolutionise the way we move goods and people around the UK.

“From 2021 the public will get to experience the future for themselves.”

In the US, the ride-sharing firm, Uber, has teamed up with Toyota in a $500m (£390m) project to develop autonomous vehicles.