Be prepared to hit the brakes a little harder if a pedestrian crosses the road.
The new law is changing the rules of the road.
The old law required drivers to yield to pedestrians and make a judgment call when to stop.
Police can now ticket motorists if they don't stop for people in all crosswalks. The fine ranges between $50 and $500 depending on the county.
It also doesn't matter if they enter when the light is green or red.
However, police say they're not spending time writing tickets up for that.
Thousands of "Yield" signs all around the Chicago area will come down. New signs informing the public about the change will go up in their place.
Chicago police told the Chicago Tribune plainclothes officers conducting stings wrote 127 tickets in August.
"The law is much clearer now," said Lt. David Blanco, commanding officer of the traffic division in the Chicago Police Department. "We know it's having an impact because people in the neighborhoods where there have been serious traffic crashes come out to the street and pat officers on the back for doing these enforcement missions."