The concept of high-speed frictionless train travel through pressurized, above-ground tubes began life as a fanciful dream -- one popularized by serial entrepreneur Elon Musk.

Last year, Musk expressed interest in an idea called Hyperloop -- a plan to propel pod-like trains through tubes at upwards of 500 miles per hour. But with Musk's energies devoted to his car and space travel projects, Tesla and SpaceX, he called on other entrepreneurs, engineers and problem-solvers take up the concept in his name.

Several start-ups sprouted. And now, one of them is announcing a significant step forward.

On Thursday, Hyperloop Transportation Technologies announced two new partners, Aecom and Oerlikon.

Aecom is a sizable and well-respected Fortune 500 engineering design firm. The publicly-traded company employs more than 100,000 people and pulled in $19 billion in 2014. Aecom has been involved in a number of large construction and infrastructure projects, including the Abu Dhabi International Airport and the Barclays Center​.

"HTT's technology is very exciting and could have a significant impact on transportation infrastructure in the future," Andrew Liu, vice president of new ventures at Aecom, told seattlepi.com.

Though it's not clear how Aecom fits into the project, Oerlikon says it will be lending at least 12 of its employees to HTT's cause. Oerlikon is a slightly smaller Swiss tech firm that's worked on a number of highly specialized projects, including providing specialized vacuum components to CERN's Large Hadron Collider.

The partnerships were announced by Dirk Ahlborn, HTT's CEO, in a press release this week.

Ahlborn also said the company would be working with architecture firm Hodgetts & Fung, and plans to have passengers on test pods by 2018.

"Our team continues to grow and, along with these new alliances, is representative of the collaborative spirit of HTT and are key to our success in breaking ground in 2016," Ahlborn said in a press release. "We receive applications from professionals and are approached by industry leading companies every day."

Earlier this year, HTT announced it had secured to rights to several acres in Quay Valley, north of Los Angeles, on which to build the company's Hyperloop test track. HTT expects to break ground there in 2016.

"We have everything basically figured out for Quay Valley, but we are still trying to continuously develop new ways of making things better or more economical," Ahlborn told Tech Insider. "The timing always varies a little bit, but we are making steady progress, and, for now, we are still in our timeline and everything looks good."

"What we are doing has never been done before, so that is a very big challenge," Ahlborn said. "Over the next couple of months, we are going to reveal some things we have been working on for quite sometime."