Driverless-vehicle testing usually involves some level of autonomous technology, but Virginia Tech university's recent experiment involved disguising a human driver as a car seat.

The unusual minivan was spotted last week on the streets of Arlington County, Virginia. It confused residents because it appeared to be self-driving, but didn't sport a visible system of lidar sensors that would typically enable an autonomous vehicle to operate.

The interior of the car looked empty at first glance, but two local news outlets, ARLNow.com and News4, captured video showing an occupant in the driver's seat – cunningly concealed in the cushions.

This is one of the strangest things I've ever seen @nbcwashington @ARLnowDOTcom pic.twitter.com/8ipKEnkeiq

— Adam Tuss (@AdamTuss) August 7, 2017

The man's upper body was entirely hidden by the car-seat costume, with his arms sticking out at waist level to discretely steer the wheel.

The strange sight came courtesy of Virginia Tech's Transportation Institute (VTTI), which admitted it had been running an experiment testing the responses of pedestrians and motorists to self-driving cars.

The institute is looking at the optimal design for autonomous vehicles, including whether there is a need for additional exterior signals. The test vehicle was fitted with a slim bar on the windscreen that would blink red when it was stopped at a traffic light and green once it was moving.

The VTTI said it had specifically designed the test vehicle, a Ford Transit Connect van, to conceal the driver while allowing them to see and move safely.

"The driver's seating area is configured to make the driver less visible within the vehicle, while still allowing him or her the ability to safely monitor and respond to surroundings," said VTTI.

"Research projects such as this (eg studying human behaviour in the presence of new technology in the real world) are extremely valuable to policy makers and vehicle manufacturers."

It tested in Arlington because the district was considered representative of the sorts of urban areas where driverless vehicles are most likely to be used. The state of Virginia approved the testing of autonomous-driving technologies on its roads in July 2017.

Apple, Google, BMW, Ford, Mercedes-Benz and Tesla are among the car brands currently conducting their own driverless-vehicle testing.

BMW board director Peter Schwarzenbauer told Dezeen earlier this year that the brand was working with psychologists to help them overcome the psychological resistance people have to autonomous cars.