The transit agency wants to spend more than $2 billion to buy 846 new 7000-series rail cars to replace old rail cars that are 30 years or older.
The changes will help to modernize the transit system to improve service and benefit customers, according to a CTA news release.
The new rail cars are expected to be delivered beginning in 2016. They will join the 5000-series cars currently being used on three CTA train lines.
By the year 2022, the CTA hopes to have a modern rail fleet that, on average, is less than 10 years old.