More than 600 new high-definition security cameras will be added to the Chicago Transit Authority (CTA) rail system in an effort to modernize and increase safety, announced Chicago Mayor Rahm Emanuel.

“The CTA is in the midst of an unprecedented modernization, from new tracks, railcars and switches to new security technology to support safe commutes for every resident on every rail line,” said Mayor Emanuel in a press conference Sunday. The new HD cameras, along with lighting improvements along the Green Line, mark the beginning of the Safe & Secure program, funded in part by a ride-hailing fee dedicated to transit.

The program will add 1,000 new cameras and upgrade more than 3,800 older-model cameras throughout the CTA system, according to NBC Chicago. The upgrades are scheduled to take place over the next five years, costing an estimated $3.5 million.

According to a news release, CTA’s security camera network has more than doubled since 2011, and the cameras have aided police in the investigation, arrest and charging of more than 1,300 individuals.