Last week, Chicago Mayor Rahm Emanuel selected billionaire tech entrepreneur Elon Musk's The Boring Co. to build tunnels that autonomous vehicles would zoom through at speeds over 100 mph to transport riders between the Loop and O'Hare International Airport.
The groundbreaking proposal would change Chicago's transportation landscape drastically.
Here are five other transportation proposals that tried to do just that, but have yet to make it off the ground:
1. A third airport in the south suburbs
A third airport on a man-made island in the middle of Lake Michigan? That was Mayor Richard J. Daley's proposal in 1958 to redevelop downtown Chicago.
Though Daley's vision never came to fruition, the idea to add a third airport to relieve O'Hare and Midway has been in the making ever since. But the more practical place that politicians have proposed over the years has been in the south suburbs.
Former Gov. Pat Quinn called for public input in 2014 to open a third airport in Peotone. At the time, the state had already spent more than $75 million to buy land for the project, but it faced pushback from airline carriers whose execs said they weren't interested.
"They bought a lot of land and through thick and thin continued to acquire parcels for a third airport, but the whole project just ran out of steam. And I think Midway's success (and) O'Hare's expansion dealt a death blow to the south suburban airport," said Joseph Schwieterman, a DePaul University professor with a focus on transportation and urban planning, and author of the book "Terminal Town."
The idea also hasn't materialized under Gov. Bruce Rauner, but in May 2017 six firms expressed interest in the project to the Illinois Department of Transportation.
2. The Crosstown Expressway
Envisioned as four lanes in each direction that would weave through the Northwest, West and South sides, the highway route was first proposed in the 1960s also by Daley.
"There's no doubt construction will start on the Crosstown," Daley said to reporters in 1963. "You can write that down."
But it never did, and the plan was quashed after concerns it would displace thousands.
"The whole development turned into a soap opera," Schwieterman said. "They were insensitive to neighborhoods."
The proposal was stopped in its tracks once again in 1986 when Mayor Harold Washington vowed the highway wouldn't be built while he was in office.
In 2007, House Speaker Michael Madigan attempted to re-envision the project as a toll road. But some expressed doubt at the time.
3. The STAR Line suburb-to-suburb commuter train
To address a boom in the Chicago suburbs, Metra proposed a commuter rail line for $1.1 billion in 2003. Trains were expected to wind through nearly 100 communities throughout Will, DuPage and Cook counties at 79 mph. The Suburban Transit Access Route, or STAR Line as it was called, would have been the first suburb-to-suburb line in the Chicagoland area.
"STAR line was a bridge too far. It was a big idea that lacked its champion to put it over the top," Schwieterman said. "It was deemed as a way to get the suburbs something in return for having a vastly expanded O'Hare in their backyard."
A fight between the Chicago Transit Authority and Metra for funding put the project in jeopardy in 2004. And after federal funding the line relied upon languished, it never gained momentum.
4. The Loop Connector
First proposed in the 1970s, the plan to build an east-west downtown train line, known as the Loop "Connector" has recently resurfaced.
It reappeared in 2009 as part of the city's Central Area Action Plan, which included a long list of billion-dollar projects to expand Chicago's transportation offerings.
"It's been cursed by political indifference and bad timing," Schwieterman said. "It seems like every time they try to do something, there's a recession or a mayor that gets cold feet."
In 2015, the question of the Connector was raised again in a study conducted by the University of Illinois at Chicago and the Chicago Central Area Committee, according to DNAinfo.
A year later, plans for the 14-mile line were submitted to the MacArthur Foundation in hopes of securing a $100 million grant for the project, according to Curbed Chicago.
5. Ferry service across Lake Michigan
The blue expanse of Lake Michigan has inspired many to propose building artificial islands in its waters to serve as vacation destinations or even as a new city.
But in 1998, Chicago was being considered to be part of a ferry highway to help provide relief to the few congested expressways that were left.
But with high costs and a lake that's frozen most of winter, ferries were unable to ride the transportation wave.
"The geography remains a problem," Schwieterman said. "That's doomed the sector, and so we're left with a magnificent lakefront with no scheduled boat service across the lake."
