CHICAGO (CBS) — Two sets of red light cameras have been installed at two busy Michigan Avenue intersections downtown, the first such devices on the iconic thoroughfare.

The city has installed two red light cameras at Michigan and Jackson, and two at Michigan and Ontario.

“These two locations have consistently scored high for potential red-light camera placement due to the high number of crashes and the unique characteristics of the intersections. Both intersections have large number of pedestrians and heavy vehicular movements which make pedestrians particularly vulnerable. Michigan & Ontario has one of the largest pedestrian volumes in the City,” Chicago Department of Transportation spokesman Mike Claffey said in an email.

While the cameras began operating on Monday, the first $100 tickets won’t be issued for violations until Feb. 5.

Signs have been installed at both intersections to warn drivers about the cameras. For the two weeks before tickets are issued, cameras will flash when a driver runs a red light as something of a warning signal.

The city said the selection of the two Michigan Avenue intersections for red light cameras is the result of a Northwestern University study that showed existing cameras at other locations would be more effective if they were moved elsewhere.

City officials said they have removed cameras at six intersections, based on the Northwestern study.

According to CDOT, before the study, the city removed 78 cameras from other intersections, based on a review of crash data showing accident rates had dropped at those locations.

Mark Wallace, with Citizens to Abolish Red Light Cameras, said the new cameras are all about revenue, not safety.

“We have all the business traffic. People are commuting into work. You have intersections that people are stuck at. There’s not people blowing through a lot of red light intersections here. This is going to be an absolute deluge of money going into the city,” Wallace said. “A 100 percent money grab where they see high rates of traffic volume, where they can rake in millions of dollars.”

Wallace said there have been four serious crashes at Michigan and Jackson in the past four years. He said the red light cameras will hurt commuters, not downtown residents, since the people who live in the area don’t regularly drive.