SEATTLE — The Transportation Department says a big construction project on I-5 in Seattle is five days ahead of schedule.

The 19-day project is on track for completion in 14 days, by August 24th. Since Friday night crews have been replacing expansion joints on a mile-long stretch of the northbound lanes between the West Seattle bridge and I-90.

Transportation officials were pleasantly surprised that the traffic congestion on the first three commuting days was not as bad as feared. They had warned for months that the work could back up traffic all the way to Tacoma. Commuters listened, and many have been choosing alternatives.

But the congestion could get worse when northbound I-5 is restricted from three to two lanes as crews move from the east to the west side of the freeway.

The department says the Thursday morning commute could be tougher.