Hand gestures, head nods and thumbs-up signals all help to ensure drivers, pedestrians and cyclists know what each other is doing.

But how will self‑driving vehicles, with no human driver, communicate with those around them?

Ford has been testing one approach that uses lights to indicate what the vehicle is doing and what it will do next as part of research into a communication interface that will help autonomous vehicles seamlessly integrate with other road users.

To ensure testing was as realistic and natural as possible, the company created the 'Human Car Seat' installed inside a Transit Connect van.

Designed to look like an autonomous vehicle, with the driver hidden in the seat, observers could more effectively gauge responses to a roof-mounted light bar that flashed white, purple and turquoise to indicate when the van was driving, about to pull forwards and giving way.

The tests concluded that 60% of 173 people surveyed after encountering the Transit Connect thought it was an autonomous vehicle. Together with the observed reactions of a further 1,600 people, turquoise - more noticeable than white and less easily confused with red than purple - was the preferred colour.

Ford is working towards ensuring that people trust autonomous vehicles. Essential to this is the creation of an industry standard for communicating driving intent. There was also a high level of acceptance and trust in the signals, providing a basis from which researchers can further develop the visual language.