During a recent TED Talk, the 45-year-old executive revealed his vision and motivation for each of his companies — The Boring Company, Hyperloop, and Tesla. There’s a lot Musk wants to accomplish in a short period of time, which begs the question: Can he actually turn his futuristic plans into reality?

Fortune spoke to several experts to see if they share the CEO’s optimism.

The Boring Company tunnels

Musk established The Boring Company in December 2016 after he complained on Twitter about traffic driving him “nuts.” According to the company’s recent concept video, the idea is to have Teslas (of course) pull up to a port stationed on the side of a busy city road, where the cars are then submerged beneath the street. Once on the underground freeway, cars would be able to travel at speeds up to 124 miles per hour.

While exciting, experts are unsure whether the proposal could actually be executed. “The chances of this coming to fruition all comes down to cost,” said Randall Guensler, a professor in the School of Civil and Environmental Engineering at Georgia Tech, adding that Musk must consider the integration of this technology with planning policy. “Who owns the roads? Who owns the tunnels? Who’s responsible for the vehicles?”

Fred Moavenzadeh, professor of systems engineering and environmental engineering at MIT, compared The Boring Company to his work on a proposed underground high-speed train in the 1960s. “The [1960s train’s] main problems were with deep tunneling and its guidance system, and what Musk is proposing is essentially a new version of that,” Moavenzadeh said of the train, which engineers had hoped could run between Boston and Washington, D.C. within one hour. “At that time we were talking 400 miles per hour with deep tunnels that could peel off and go to Hartford, for example, but we were always concerned with what would happen if the train got stuck — how would we evacuate the people from those depths, in that air pressure?”

Hyperloop train

Musk thinks it’s possible to utilize the Hyperloop — his proposed above-ground rapid transit system that would propel passenger pods at airliner speeds — in The Boring Company’s underground tunnels as well. “There’s no real length limit,” he said, adding that the Hyperloop’s technology could be useful for routes between Washington, D.C. and New York City.

Hebert Einstein, a professor at MIT’s Department of Civil and Environmental Engineering, doesn’t necessarily disagree — it’s just not a new concept, he said. “If you look at [the] history of New York City tunnels, the idea of a subway that goes through partially low-pressure tubes is certainly doable. That concept is 100 years old,” he said.

But Guensler has some questions: “You build deep tunnels, but now you have to reintegrate vehicles back above-ground. You’re not just building a tunnel, but a port interchange from a moving system underground to above-ground delivery,” he said, explaining that existing infrastructure like subways and highways on the surface must be accounted for.

Autonomous cross-country travel

Musk said Tesla is still on track to develop fully autonomous cars capable of driving from New York to Los Angeles by the end of the year. This would mean a Tesla could go from a parking lot in California to a parking lot in New York without being touched at any point, the CEO said.

It’s a tall order, and Tesla has just under seven months to fulfill that promise. But Pablo Durango-Cohen, an associate professor of civil and environmental engineering at Northwestern University, says it’s definitely possible. “That’s easy,” he said. “Uber already has fully autonomous vehicles in urban areas like Pittsburgh. Long-distance trips on interstate highways are easier than urban trips. All that is needed is some money to finance service infrastructure, if needed.”