The CTA is suspending service for two, nine-day periods from early March to early May because of the reconstruction of the Wells Street Bridge.
The 77,000 people per-day travel on trains that cross the river on the Wells Street Bridge will all be impacted.
"The line cuts will affect the Purple and Brown Line service on weekdays, resulting in reduced capacity on the Red and Brown lines during the peak of the weekday rush periods," CTA President Forrest Claypool said.
The reconstruction of key components of the double-decker bridge will seriously impact service over two periods: March 1 through the 10 and again from April 26 through May 5.
"It's a big deal because I work downtown and take this every single day coming home so it'll definitely make a big difference," Brown Line rider Miranda Domingo said.
During that time Purple Line service won't run south of Howard.
Two of every three Brown Line trains will divert to the underground Red Line tracks after Fullerton.
One of three Brown Line runs go to the Merchandise Mart but stop there.
"I'd like to encourage our customers to plan ahead. Allow extra commuting time during this bridge reconstruction project," Claypool said.
The CTA will offer free transfers to a temporary train shuttling customers around the Loop.
There will also be extra Red Line trains and bus shuttles along the Brown Line route.
Commuters like Robert Flint are concerned about whether the CTA's alternates will be enough?
"I just don't have a lot of confidence in getting to where I need to go all the time when they're cutting back on services I depend on," Flint said.
Nonetheless the city is promising short-term pain will be long-term gain.
"When we're done we will have extended the life of that infrastructure for about another 50 years," Chicago Department of Transportation Commissioner Gabe Klein said. "So it's a little bit of pain - and we appreciate the public being patient with us - but it'll be worth it."
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