Police say the cameras are crucial to capturing people who open fire on roadways, a problem that's surged this year.
It has been more than two years since Tamara Clayton was shot and killed on Interstate 57.
"She was driving to work and she was shot multiple times," said her sister, Alma Hill.
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The expressway cameras installed at the time were low definition and could not record, so Clayton's murder went unsolved.
"Nothing for the state police to work with at all, nothing," Hill said.
Ever since her death, the family has been working to change that. Last year, Governor J.B. Pritzker signed the Tamara Clayton Expressway Act. The grant gave $12 million to install high-definition cameras with license plate reading equipment. Finally, the process began this week.
"They are starting in Cook County and the areas around Chicago," Hill said.
"When we know that shooting has taken place, we'll be able to track somebody who, from whose car that shot has been taken," Pritzker said.
So far this year, Illinois State Police have responded to 157 shootings on Chicago-area expressways.
The number is at least three times higher this year, than last.
"These are people with names, families, and that is what we have to understand," Hill said.
Clayton's sister hopes the new technology will help save other innocent lives.
"I want a more sense of urgency," Hill said. "I appreciate the cameras are here, but how are you going to use them going forward?"
The high-definition license plate reader cameras will be installed in Cook County first, and then rolled out across the rest of the state. The project is expected to take several months.