Workers will close the westbound Interstate 105 offramp onto Sixth Avenue for about four weeks starting Monday morning as they continue major construction on the freeway between Delta Highway and Seventh Avenue.

The Oregon Department of Transportation said motorists should expect lane closures on I-105 in both directions through the end of August.

The westbound I-105 speed limit approaching the work zone is now 45 mph for safety. Eugene Police Department is providing extra patrols in the area.

The bumpy ride is from new bridge joints that workers have installed. The ride will smooth out when the corridor is paved in September.

State transportation officials note it's likely increased tie-ups will continue, especially during the evening commute hours, on I-105 as well as Country Club and Coburg roads and through the Ferry Street Bridge area.

The ramp and lane closures are needed as crews continue the two-year, $18 million project to modernize the aging stretch of I-105, which connects downtown Eugene with Interstate 5 and Springfield. The corridor carries an average of 60,000 vehicles daily.

The construction work involves installing new bridge rail, joints and lights, making other repairs, completing a seismic retrofit, and paving the roadway.

Once the ramp upgrades are complete this fall, crews will shift to the last phase of the two-year, $18 million project to upgrade the Willamette River bridge.

Officials urge motorists to visit www.tripcheck.com.