It's Curious City, where we take your questions about Chicago and the region, and investigate, report, explore, from WBEZ.

It's a sunny Thursday afternoon, and I'm in the car with question-asker, Alyssa Gitlow.

She's on her normal afternoon commute home from Hyde Park to the north side,

and traffic is backed up as far as the eye can see.

Alyssa, when do you think we're going to get any relief from this northbound traffic on Lakeshoree Drive?

I anticipated that it would start at McCormick Place, and it did, and it will stop at Chicago Avenue.

Why Chicago Avenue? Because there's an exit there at Chicago and the Lake with no ramps.

Instead, people get on and off there using a stoplight. It's not your average stoplight, though.

The Chicago Avenue lights

turned off during the morning rush hours, letting the area operate like a regular highway.

But then it's turned on the rest of the day, including the afternoon rush. And that slows afternoon

traffic to a crawl, delaying hundreds of thousands of commuters a week. For Alyssa, it means her morning commute

is a breeze, while the commute home can be an hour-plus nightmare. So she wants to know,

why is the stoplight turned off in the morning at Lakeshore Drive in Chicago, but is turned on

in the afternoon backing up traffic for miles.

We asked Jeffrey Sriver at the Chicago Department of Transportation.

He says in the afternoon, the entrance is crucial to folks who work in big institutions around it.

Think a university and two hospitals.

People need to get from Chicago Avenue to the northbound lanes.

And so we have to balance those demands, the demands of the people who are coming from further south and then have to

stop to let that traffic go. But Alyssa asks why workers can't just scoot over a few blocks to Oak

in Michigan or Grand. Surrevers says, there's already quite a bit of traffic on North Michigan

...