There was concern that all train traffic in the area would be shut down. The Secret Service says Metra, South Shore and Amtrak trains will run during the summit, but they may not all be on schedule.
Dozens of South Shore and Metra Electric trains pass beneath McCormick Place every day carrying thousands of passengers to and from work.
While the Secret Service has decided that commuter train service during the NATO summit will not be closed to riders, at the same time they are suggesting that it will not quite be business as usual.
In a written statement, the Secret Service says that "passengers should plan for some delays as trains approach and pass through the McCormick Place stop due to security measures."
What those security measures may be - whether involving possible passenger screening or station closings - the Secret Service isn't revealing, at least at this point. But the decision to keep the trains running, particularly on Monday, May 21, is reassuring to commuters.
"I'm relieved that they're not going to cut off the service for the NATO meetings," said John Holmberg, Metra Electric rider.
"I'm probably not going to be doing any visiting," said Michael Myers, Metra Electric rider. "I'm probably going to stay away from it, away from downtown and just avoid it. I'm going to avoid it."
"For security, I think as long as people feel safe, passengers feel safe as well as the higher up officials, that's what matters," said Katie Britton, Metra Electric rider.
The Secret Service has also published bidding specs for the temporary security barrier it plans to erect around McCormick Place. Where precisely the fencing will go has not yet been revealed, but the specs call for steel fencing as well as concrete barricades, and they suggest that at least some of the barrier construction will begin as early as a week ahead of the summit's beginning.
Pittsburgh, which hosted the G20 in 2009, and Toronto, which hosted the following year, each had an inner security perimeter which allowed only credentialed pedestrian traffic, and an outer perimeter which kept vehicular traffic at a distance.
Every city that hosts a global summit has unique challenges. The security perimeter in Pittsburgh for the G20 was a fairly tight one, and it's expected that the Secret Service will attempt to design as tight a security perimeter as possible for NATO weekend here. Exactly what that is we won't know most probably for a couple weeks. The Secret Service didn't reveal its specific security plans for Pittsburgh until two weeks before the event.