Have you noticed those concrete barriers lining Market Street in Center City?

Well, get used to them.

For the next 12 to 18 months, the barriers will create a pedestrian walkway as construction crews start demolishing portions of the walls of the old Gallery shopping center, said Pat O'Donnell of the city's Streets Department.

The barriers are a street-level signal that the next phase of the $575 million renovation has begun.  The first phase of transformation of The Gallery -- into the Fashion Outlets of Philadelphia -- began earlier this year with internal improvements.

The barricades are set to line 8th, 9th and 10th streets, as well as a portion of 11th Street.

They are also going up on Market and Filbert Streets, between 8th and 11th.

"The request was for permits to close off portions of the roadway in order to allow this work to continue," O'Donnell said, adding: "The original request was full sidewalk closure, but with this location there was no way we were going to approve that."

So the city created a plan with contractors Shoemaker and Skanska to maintain pedestrian pathways around the perimeter of the project.

The walkway will cut into a traffic lane on Market Street, but O'Donnell said traffic patterns will not be affected on Filbert, or any of the numbered streets.