The trial, conducted with the Virginia Tech Transportation Institute, also made use of a light bar mounted on the top of the windshield to provide communication about what the auto was doing, including yielding, driving autonomously or accelerating from a full stop.
It had someone in the driving seat wearing a auto seat costume to fool pedestrians and other drivers, and research how people react to driverless cars.
"Understanding how self-driving vehicles impact the world as we know it today is critical to ensuring we're creating the right experience for tomorrow", John Shutko, Ford's human factors technical specialist, said in a statement."We need to solve for the challenges presented by not having a human driver, so designing a way to replace the head nod or hand wave is fundamental to ensuring safe and efficient operation of self-driving vehicles in our communities".
Researchers rejected the use of displayed text because of potential language barriers, and symbols due to their low recognition.
The specially outfitted Transit Van logged 1,800 miles in August, much of it in and around Arlington, Va., including urban intersections, parking lots and garages.
Instead, they settled on visual signals from a light bar placed on the windshield of a Ford Transit Van.
Three different light signals were used to indicate the auto meant to yield (two white lights moving side to side), when it was engaged in active autonomous driving (solid white light), and when it was starting to go (a rapidly blinking white light to indicate the vehicle is about to accelerate from a stop).
The van was piloted by a human driver, who wore a camouflaged "seat suit" to simulate a driverless vehicle.
The aim of the exercise was to capture on video human reactions to both a self-driving vehicle and to the light signals from the windshield.
The research project looked into the most effective way for enabling communication between a self-driving vehicle and other road users. The company is working with an industry group and other automakers "to try to gain global consensus".
Ford has set a target of putting a self-driving shuttle into commercial ride-sharing fleets by 2021.