Elon Musk — the restless billionaire behind Tesla, SpaceX, and SolarCity — was stuck in annoying traffic and mused that one solution would be to drill more tunnels. All he’d need, really, is a giant machine…
Everyone’s trying to figure out whether Musk is genuinely serious about starting a brand-new tunnel-boring company or not. Who knows! But tunnels are fun to think about, so why not pretend he is serious and think through how this might actually work….
One obvious hitch to Musk’s scheme is that some cities are already trying to dig new tunnels to accommodate traffic — and it’s far from easy! There’s a lot of existing infrastructure buried in the ground beneath cities, from water mains to electrical cables. And the tunnels themselves often need to be reinforced. That makes tunneling slow, difficult, and expensive work.
Seattle is a cautionary tale here: Since 2013, the city has employed a massive 57-foot-diameter boring machine named Big Bertha to drill a 2-mile highway tunnel beneath the downtown area. Yet six months after work began, Big Bertha broke down after overheating. Drilling finally resumed in late 2015 — but then had to stop again after a sinkhole opened up near construction. Perhaps Musk can improve on Big Bertha. But that brings us to an even deeper problem with his idea. Building more tunnels is just not a good way to alleviate traffic congestion. In fact, it would likely do the opposite.
The “fundamental rule” of traffic: building new roads just makes people drive more
In January 2016, during SpaceX’s Hyperloop pod design competition, Musk explained why he thought tunnels could help alleviate traffic:
It’s a really simple and obvious idea and I wish more people would do it: build more tunnels. Tunnels are great. It’s just a hole in the ground, it’s not that hard. But if you have tunnels in cities you would massively alleviate congestion and you could have tunnels at all different levels — you could probably have 30 layers of tunnels and completely fix the congestion problem in high-density cities. So I strongly recommend tunnels.
Except economists and traffic experts have been studying this issue for a long time and they’ve found the exact opposite. When cities add new roads to a congested area, it usually doesn’t alleviate congestion. Instead, it just induces more traffic, as people take advantage of the added road space to drive more.
Granted, there can still be good reasons for fast-growing cities to build new roads. They just shouldn’t necessarily expect traffic jams to disappear as a result. Los Angeles got a firsthand glimpse of this after widening its I-405 freeway, a project that cost $1 billion. “The data shows that traffic is moving slightly slower now on 405 than before the widening,”
So what does help alleviate congestion? If cities really want to erase traffic jams, many transportation economists would instead recommend that they charge people to use roads when they’re crowded — a policy known as congestion pricing that has popped up in places like London, Singapore, and Stockholm.
Early research suggests that pricing really does cut down on traffic, as people decide to move their commutes to non-peak hours, shift to mass transit, or cut down on trips overall. It’s arguably even more effective if cities use the funds to provide alternative transportation options.
The downside is that congestion charging tends to be rather unpopular, since people don’t like it when they suddenly have to pay for something that used to be free. (It’s the same reason why checked-baggage fees on airplanes have incurred such a backlash.) So urban planners tend to favor building new roads and widening existing roads — or, in Musk’s case, new tunnels — even if the research suggests again and again that it doesn’t cut down on congestion.
Now, that doesn’t mean a tunneling machine would be useless! Remember, Musk also has plans to start colonizing Mars within a decade. And humans living on Mars would probably want to spend most of their time underground to avoid the higher levels of solar radiation that hits the planet.