(CNN) A gray van was recently seen cruising the streets of suburban, Washington, D.C. -- without a driver.

But this wasn't one of those self-driving cars that Google and car companies have been testing. This was ... something else.

The unmarked van first appeared in a video on ARLnow.com , an Arlington, Virginia, news site. In the video pedestrians comment on the van, clearly realizing something is up.

That's when a local reporter decided to dig deeper . WRC TV's Adam Tuss and his photographer followed the van for 20 minutes, even after he says the van tried to lose them.

Tuss finally caught up with the 2017 Ford Transit Connect and peered through its windows, only to find a person inside.

But instead of sitting in the car's seat, the person was the seat. The driver was dressed in a car-seat costume.

I tried talking to the driver - but he blew through a red light and drove off. Could this all be a prank??? @nbcwashington pic.twitter.com/bn72daBNUA — Adam Tuss (@AdamTuss) August 7, 2017

"Could this all be a prank???" Tuss tweeted, along with a video of the encounter.

But no, it was not.

What had everyone fooled was actually a university research project.

Mysterious sightings

The story started when Scott Brodbeck, editor and founder of ARLnow.com, walked outside his office to take a phone call.

He didn't really think much of it when he saw an unmarked gray van drive by him. That is, until he realized he hadn't seen a driver inside.

"On a hunch, I stayed there hoping it would return so I could take another look -- and sure enough, it did," Brodbeck told CNN.

The van drove by him no less than four times before he became sure of what he'd seen. He filmed video on his iPhone and headed back inside.

A few days later, Tuss journeyed to the Arlington neighborhood where Brodbeck had seen the car. After talking with Brodbeck, he walked out of ARLnow.com's office and spotted the van himself.

Alert!!! We found the supposed self driving van in Arlington - and there's a guy hiding behind the seat!!! @nbcwashington pic.twitter.com/EeI7rhQi1R — Adam Tuss (@AdamTuss) August 7, 2017

Tuss and the WRC photographer began to follow the van. At one point, he says the van even ran a red light trying to lose them.

Tuss walked up to the car and knocked on the window.

He first saw what he thought was an empty seat. Then, he saw a man's hands and legs.

Here's me trying to talk to a man in a car seat costume @nbcwashington pic.twitter.com/e5humOM7uS — Adam Tuss (@AdamTuss) August 7, 2017

"Brother, who are you? What are you doing? I'm with the news, dude," Tuss says in the video. "Dude, can you pull over and we can talk for a second?"

But there was no response from the man inside the seat.

This is one of the strangest things I've ever seen @nbcwashington @ARLnowDOTcom pic.twitter.com/8ipKEnkeiq — Adam Tuss (@AdamTuss) August 7, 2017

Not a prank

At this point, you're probably wondering why the man inside the van was wearing a car seat.

Brodbeck was wondering, as well.

He thought the van was with the Virginia Tech Transportation Institute, but a spokeswoman there told him she had no comment.

However, the same spokeswoman, Anne Deekens, told CNN that the van was indeed related to VTTI's research on automated vehicles.

"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," according to a VTTI statement.

The Institute released information about its study on Monday, the same day Tuss found a man inside the van.

Researchers say the study was aimed at determining how to design automated cars.

The Arlington area was selected for the study because it's "representative of the urban areas for which automated vehicles are currently being considered," the statement says. It also says Arlington County officials were consulted in planning the study.