This is the first weekend that train service is being suspended so work can begin.
By the time the project is done in 2018, Eyewitness News is told the ride from downtown to O'Hare will be 10 minutes faster.
Starting at 10 p.m. Friday, no trains will stop between the Western and Logan Square stations. A free shuttle bus will be offered to passengers instead.
The work includes replacing wooden rail ties and other track materials. Over 10 weekends between now and August, sections of the Blue Line will be closed.
The CTA says the four-year, $492 million project will improve 12.5 miles of track and signals and overhaul 13 stations from O'Hare south to Grand, reducing slow-zones and giving a much-needed makeover to one of the oldest CTA branches.
"We said what does it need? It needed new track work to be faster. It needs stations that are more modern, better lit, etc., more accessible," said Tammy Chase, CTA spokesperson.
The work will be done on select weekends from 10 p.m. Friday nights until 4 a.m. Monday mornings. And this weekend, the Logan Square, California and Western stops are affected, with riders having to get off trains and take shuttle buses between those stops.
"Allow extra travel time. We'd say about 20 minutes extra to get to work or your flight on time," said Chase.
The project comes on the heels of the Red Line South overhaul, which shut down the entire branch for five consecutive months. The CTA says this project is much different from station to station, and that's why it is being spread out over four years.