CHICAGO (CBS) — A year after a disastrous attempt to begin bridge replacement work on the Union Pacific North line in a two-mile stretch of Chicago’s North Side, Metra is about to try again.

As WBBM Newsradio’s Bob Roberts reports, Metra found out quickly last September that leaving only one track in service, to carry trains in both directions, would never work. On-time performance dropped precipitously and so did ridership, which took months to recover.

LISTEN: WBBM Newsradio’s Bob Roberts reports

This time, Metra says it has learned its lessons. Spokesman Michael Gillis said there will be no attempt to funnel trains from both directions down a single track.

“During construction both tracks on the UP North line will be operational and rush-hour commuters should not be impacted by construction activity,” Gillis said.

Gillis said most work will be limited to midday hours. Some delays are possible then. He said the bridge at Sunnyside Avenue (4500 north) will be the first replaced, followed by those at Berteau Avenue and Grace Street.

Other bridges in the first phase will include those at Balmoral, Foster, Winnemac, Lawrence, Leland, Wilson and Montrose avenues, and Irving Park Road.

Bridges between Addison Street and Webster Avenue will be replaced between 2015 and 2019.

All of the bridges being replaced are more than 100 years old, and Gillis said Metra believes it is no longer possible to repair and maintain them economically. The new bridges are expected to last 100 years.

The project will take eight years to complete. It also includes a totally new station at Ravenswood, the most heavily-used stop on the line outside of Ogilvie Transportation Center.

The way the line is rebuilt will allow Metra future options to expand the number of tracks to four, which would allow it more options for express trains.

The portion of the line on which the bridges are being replaced had three tracks as recently as the early 1980s.

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