CHICAGO (CBS) — On the heels of a major overhaul of the Dan Ryan branch of the Red Line, the CTA is planning a nearly half-billion-dollar upgrade of another busy train line: the Blue Line to O’Hare International Airport.

CBS 2’s Mike Puccinelli reports the city and the CTA plan a 4-year, $492 million reconstruction project – the first overhaul of the O’Hare Blue Line in 30 years.

The announcement comes less than two months after the CTA finished rebuilding the Red Line South – replacing the tracks and renovating stations south of Roosevelt – which forced a five-month shutdown of every station along the Dan Ryan branch.

Mayor Rahm Emanuel said the renovation is a much-needed project for one of the CTA’s busiest lines, and will make the Blue Line “world class.”

CTA President Forrest Claypool said the project “will improve capacity, reliability, and speed for the 80,000 commuters who use this section of the Blue Line each weekday.”

Like the rebuilding of the Red Line, the Blue Line project will include replacing existing tracks, renovating stations, improving subway infrastructure, and upgrading power systems.

The project should shave 10 minutes off the trip from downtown to O’Hare.

This project, however, will take much longer to complete, as it does not appear the CTA plans to completely shut down the Blue Line to get the work done – which was how they were able to completely overhaul the Dan Ryan branch of the Red Line in only five months. Switch work will require some weekend shutdowns of the Blue Line.

Claypool said work on the Blue Line would be very different, and because it serves O’Hare, shutting it down completely for several months isn’t an option.

“Obviously, O’Hare Airport is the economic engine of the region, and it’s critical to commerce, and tourism, and everything else,” He said. “You can’t close the line to the airport.”

Emanuel said the overhaul will be worth the four-year wait.

“The new Blue reflects the communities that are developing along the Blue Line,” the mayor said. “When you have a 25 percent growth along the Blue Line – its usage – there’s a revitalization of our neighborhoods, and the Blue Line must continue with that revitalization.”

The Forest Park branch of the Blue Line is not part of the renovation project.

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