Elon Musk's Tunnel Could Make LA's Traffic Worse | Popular Science

Sarah Fecht at Popular Science writes: Elon Musk's Tunnel Could Make LA's Traffic Worse, or a Toll Road. I get quoted. The puns are mine.

Elon Musk is a man who makes the future happen. He's building solar panels, and electric cars that can run off of the clean energy they create. He's helping humanity become an interplanetary species by making spaceflight dramatically cheaper. But his idea to build a tunnel to avoid traffic congestion in Los Angeles seems uncharacteristically outdated.

In December, the billionaire tweeted that L.A.'s traffic “is driving me nuts. Am going to build a tunnel boring machine and just start digging.” At the time it seemed like a joke, but this week he posted an update:

The Guardian confirmed that Musk's people have been talking to folks in the city government, but no permits have been issued so far. There aren't many other details.

Perhaps the tunnel would be a private entrance to his Tony Stark-like lair. If so, Musk might be better off just taking a helicopter to LAX. Tunnel-boring is not cheap, and permitting can be a nightmare.

“If he wants to build a tunnel on his own land, more power to him,” says David Levinson, a transportation engineer at the University of Minnesota. “If he wants to build it under other people's land, he will find infrastructure construction is a slow, boring process.”

And if Musk is planning to make the tunnel open to the public, he may be in for more disappointment. About 20 years ago, civil engineers and urban planners started realizing that building freeways and tunnels was only making traffic worse.

Adding new arterial roads makes driving easier and less infuriating, so people are more likely to make unnecessary trips and choose driving over public transit. It's called induced traffic. New arterial roadways can lower traffic initially, but within a few years, congestion basically returns to its original levels of torture.

Researchers are trying to quantify the relationship between road expansion and induced traffic. Depending on the area, for every one percent increase in the miles of lanes in an area, there may be a 0.6 to 0.9 percent increase in traffic.

The new roadways can also cause traffic congestion on roads that are upstream and downstream of the new project, says Levinson.

It's worth noting that induced traffic studies aren't perfect, because studying cities is hard. A lot of the data is correlational. It wasn't collected expressly to test how a new roadway affects traffic, so it can't definitively prove that a city's addition of a roadway caused a traffic increase. And there are any number of variables that can affect where and how much people drive—from new shopping complexes and housing developments to the presence or absence bike lanes and sidewalks—so devising a well-controlled urban experiment is difficult.

However, “[t]here is no question that road improvements prompt traffic increases,” writes Robert Cervero, a professor of city planning at UC Berkeley.

Those traffic increases can also come with increased likelihood of car crashes and pollution. “Though if everyone is driving a Tesla powered by a Solar City panel,” Levinson jokes, “I suppose the pollution issue is minor.”

Public transit might seem like a better investment, but it has similar problems. Expanding capacity on public transit induces more traffic, with only a small portion of redirected from automobiles. Although it serves other important societal functions, it doesn't actually have much of an impact on road congestion, says Levinson.

He thinks that if Musk wants to relieve congestion, his best bet may be to make his tunnel a toll road. “Adding capacity without doing that is throwing money down a hole."

Some additional thoughts:

A tunnel is just a link, it's no different than any other limited access highway from a transport perspective. They tend to be costly (which is why there are so few). Of course they don't require taking much surface land (some for entry, exit, and ventilation) so there is savings there, and they are less unpopular. How much travel time savings and for whom depends very much on the context.

In general adding capacity, by lowering the cost of travel, increases the number of trips that are made and their length. (Just as lowering the cost of Cigarettes increases the number smoked). This is not inherently a bad thing, it means more people can do what they want with their time, but it means more traffic congestion on upstream and downstream links that may not have been expanded (and less congestion on parallel links that serve similar markets).

Implementing road pricing would relieve congestion (although it is obviously politically difficult).

The purpose of public transport is to serve PT passengers, not relieve congestion. (See https://transportist.org/2015/05/13/for-whom-is-transit/ )  It should not be invested in "to relieve congestion" but to provide access for transit users. It has the same types of induced demand effects anything else does, if there is more capacity in times which are constrained, it will attract new demand (with an elasticity similar to road expansion), only a small share of which will come from roads. And those who switch from roads will free up capacity that will be used by others switching into the peak (with an elasticity similar to road expansion). This does not mean investment is inherently a bad thing, it gives people more choices, but transit's effect on road congestion is really limited, especially in a place like LA (or most of the US for that matter). Similarly we should not expand roads to relieve transit crowding.

If he aims to make money at this venture, it will be very difficult without public subsidy.