Virgin Hyperloop announced Sunday that humans have traveled in its superfast vacuum tube for the first time, albeit at limited speeds.

The futuristic mode of transport, which involves firing a pod through a low-pressure tunnel, was tested by the company’s Chief Technology Officer Josh Giegel and Sara Luchian, who is director of passenger experience.

On Sunday afternoon, they travelled 500 meters in 15 seconds on a test site outside Las Vegas, where the company has already completed over 400 unoccupied tests.

They reached around 100 miles per hour (160 kilometers per hour), which is some way off the 1,000-kmh-plus speeds the company hopes to achieve, but it still marks a significant step forward for hyperloop fans. By way of comparison, China has magnetic levitation trains that run at 268 mph between Shanghai and Pudong airport.

Richard Branson, founder of the Virgin group, said in a statement: “With today’s successful test, we have shown that this spirit of innovation will in fact change the way people everywhere live, work, and travel in the years to come.”

Hyperloop uses electric propulsion and electromagnetic levitation in near-vacuum conditions to transport pods from A to B.

In 2013, Tesla founder Elon Musk in 2013 said it would allow people to travel from Los Angeles to San Francisco in about 30 minutes. At the time, many said the idea would remain science fiction.

Other firms are also racing to develop the hyperloop concept, but Virgin Hyperloop is the only company to have successfully tested the technology with passengers.

“When we started in a garage over six years ago, the goal was simple – to transform the way people move,” said Giegel, who co-founded Virgin Hyperloop. “Today, we took one giant leap toward that ultimate dream, not only for me, but for all of us who are looking towards a moonshot right here on Earth.”

While the scaled-back test is a step towards making hyperloop a reality, it’s still not clear if the concept will be safe at full speed.

Virgin Hyperloop, which has raised over $400 million from investors including the Virgin Group, says the transportation method will be faster, safer, cheaper and more sustainable than current modes of transport.