BOSTON (CBS) — If you’re heading out to Boston Friday night or over the weekend, expect fewer open lanes of travel on the Mass Pike.

Construction on the Commonwealth Avenue Bridge will result in just one lane of travel that will be open on I-90 westbound after 8 p.m. and until 5 a.m. Monday, Highway Administrator Jonathan Gulliver said Friday.

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By 5 a.m. Monday, I-90 will be restored to its full capacity of four lanes of travel in each direction, marking a “major milestone” in the project, Gulliver said.

Commonwealth Avenue Bridge Construction on Monday (WBZ-TV)

MassDOT has asked drivers to take a different route if possible to avoid heavy delays. Gulliver said drivers are continuing to heed warnings on driving through the area.

“The public has been very cooperative,” Gulliver said.

The Pike has seen a 40 percent reduction in traffic volume this week during construction, he added.

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But travel times have increased — up to 2 hours in some instances, he said.

Crews tore down a portion of the Commonwealth Avenue bridge on Saturday. (WBZ-TV)

Off-peak and overnight lane closures will continue to be necessary throughout the coming weeks as crews conduct finishing work.

Other closures include:

  • Memorial Drive in Cambridge, between Western Avenue and Mount Auburn Street, will be closed to vehicles on Sunday, from 11 a.m. until 7 p.m.
  • I-90 eastbound on-ramp from Cambridge Street/Soldiers Field Road is closed during construction.
  • I-90 westbound Exit 20 off-ramp to Brighton/Cambridge will be closed intermittently.
  • Commonwealth Avenue section and Boston University Bridge is closed to vehicles.

Thursday night, crews began removing the existing steel beams on the final span of the Commonwealth Avenue Bridge and continued installing closure pours, which are pours of concrete that seal in precast deck panels.

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These closure pours continued throughout Friday along with work on the concrete backwall and utility operations. Crews on Friday were also expected to be completing demolition activities and beginning to place steel beams on the final span of the bridge.