O'HARE — Workers have already broken ground on a project set add a new lane to the Kennedy Expy. in each direction near O'Hare Airport, aimed at improving safety along a collision-prone stretch of highway.
State transportation officials first proposed adding the extra breathing room in 2014, saying drivers merging from the Jane Addams Tollway (I-90) were stuffing into a bottleneck and causing collisions. As it is now, they said, the section sees a traffic accident roughly every 36 hours.
The first of three phases — with a $22.9 million price tag — is expected to be completed in November 2017, with the bulk of the work scheduled for the spring and summer, according to a statement from the Illinois Department of Transportation.
But a chorus of public transportation advocates is warning that the new lanes could just attract more traffic in the long run, opening the door to even more fender benders — or worse.
"There's been a lot of research on this, and the data bears out that if you add capacity to roads, that capacity is just going to be filled with more cars," said Kyle Whitehead, the government relations director of the Active Transportation Alliance. "When you're talking about more than $20 million in public funds, you have to be asking whether this is the best way to improve transit."
The alliance fiercely advocates for better bike and pedestrian access across Chicago, favoring improvements to public transit over new highway capacity.
"Our argument with highway investment at large is that you have to look at the cost-benefit analysis," Whitehead said. "You're encouraging sprawl and unsustainable development, and you may not gain anything in return."
The group has made a similar argument against adding new lanes to the Stevenson Expy., citing a principle that transportation researchers call "induced demand."
What is 'induced demand?'
It sounds intuitive: more space means less traffic. But the laws of supply and demand say otherwise, according Daniel Kay Hertz, a former researcher and writer for the City Observatory.
"People choose whether or not to drive to O'Hare based on what's the fastest way to get there," said Hertz, who now works for the Center for Tax and Budget Accountability. "So if it starts to get faster, people will start to say 'Let's hop on the expressway, they just added another lane.'"
"It's like water flowing to the lowest point — demand will fill whatever container you give it," he said. "So you'll be adding capacity, but give it a year or two, and each individual driver won't be going any faster."
Real examples of "induced demand" have played out in different parts of the country.
Perhaps the most extreme example was near Houston, where officials responded to chronic traffic jams along the Katy Freeway by embarking on a multi-billion-dollar project to add more lanes. By 2011, the highway had 23 lanes, making it the widest in the world.
The new space eased congestion for a time, but the volume of cars on the highway rocketed up over the next few years, according to a review of data by the City Observatory.
How could adding lanes impact traffic safety?
Illinois Department of Transportation officials drew up their plans for the Kennedy lane additions after a year-long study of traffic patterns between Harlem and Cumberland. Between 2007 and 2011, the study concluded, the stretch saw 1,083 total crashes, causing 150 injuries and four deaths.
Adding the new lanes would "give cars more room and time to merge," according to a statement from Gianna Urgo, a transportation department spokeswoman.
"That would potentially alleviate travel times throughout the region and have safety implications as well," Urgo added.
The added space isn't the project's only selling point, either. The plan calls for "improved ramp geometrics" to make for safer merging, and a later phase of the project will install sound barriers to limit noise coming off the highway.
But if the "induced demand" phenomenon holds true, it may not be a given that increased road capacity will create more buffer between cars. And even if it does, Hertz said, the simple fact of adding more cars would likely still lead to more crashes.
"By far the safest place to be, in terms of injury or death, is anywhere but inside a car," Hertz said, citing the roughly 30,000 Americans killed in car crashes every year. "So I'm skeptical that the way to increase safety is by putting more cars on the road. Even if the risk goes down for each individual driver, you could see more crashes overall."
How to cut traffic, if not by adding highway space?
For the underlying question of how to lighten expressway traffic, advocates like Whitehead have a simple answer: give people better incentives to take public transportation instead.
"Comparing public transit to road options can get complicated, but we know from research that if you have a transit option that's directly comparable, upgrading it can seriously improve congestion," Whitehead said.
In the case of the Kennedy, of course, transit isn't just comparable — the CTA Blue Line literally runs through it, running in the middle of the expressway from Kimball Avenue all the way to O'Hare.
In the meantime, another lane for the Kennedy will mean a higher volume of people headed to and from the airport. But they shouldn't expect to get there any faster, Whitehead said.
"When you look at the metrics that IDOT is using, it really just seems like they're interested in moving as many vehicles as possible," he said. "But I'm hopeful that we can get them more interested in adding new modes, too."
For more neighborhood news, listen to DNAinfo Radio here.