New technology has been the key to Elon Musk’s success as a business leader, but one of his latest ventures -- a plan to deal with Los Angeles’ traffic congestion -- shows that even the newest technology has its limits when confronting age-old problems.

Musk’s idea is to build a 2.7-mile tunnel on L.A.’s Westside under Sepulveda Boulevard. Cars would use it by driving onto a “skate” at ground level. The skate would be lowered into the tunnel on an elevator, and then would be whisked along at speeds of more than 100 mph to the car’s destination.

Even though the tunnel system is a private venture, Musk is asking for the help of state and local officials in bypassing or expediting environmental reviews for the project. The Los Angeles City Council has approved the route and said it is exempt from state environmental reviews, but two neighborhood groups have sued to reverse that decision.

Most transportation experts, however, are dubious that Musk’s tunnels will ever live up to his promises -- if they get built at all. One common criticism is that the queuing system for cars could create huge bottlenecks on existing streets. It won’t matter how fast the vehicles travel underground if there’s a long wait to even get into the system. “Enjoy the lines at Disneyland? You’ll love Elon Musk’s idea for transit,” warned one Los Angeles Times op-ed.

A similar debate is taking place in Chicago, where Musk has floated a different high-speed transit plan that would work with trains but would also involve an elaborate tunnel.

To build a bigger network of tunnels in L.A., Musk and his Boring Company would have to go through environmental reviews that would likely take years and could reveal unforeseen problems. What’s more, tunneling through Los Angeles can be tricky, given that it is an earthquake-prone area with lots of abandoned oil wells. Neighborhood groups and cities may decide to block construction on those grounds alone. In fact, Musk’s test tunnel stops just short of Culver City because of environmental opposition from city officials there. And securing the right-of-way, even underground, promises to be complicated.

Los Angeles Mayor Eric Garcetti seems undeterred. “Who knows whether it will hit or not, but isn’t it worth trying?” he says. “And don’t we as Americans want to see our technologies work and then be applied right in our own backyard instead of China or Dubai or other places that seem to be more risk-taking?”