Crews shut down two right northbound lane of Interstate 5 on Thursday night in preparation for the switch which, transportation officials fear, may snarl the Friday morning commute.

Only one northbound lane will remain open until 5 a.m. Friday, when crews will open a second lane for the morning commute.

Friday will be the first time drivers will have to face the morning commute with just two northbound lanes of I-5 open. Up until now three lanes have been open, but additional closures are necessary for crews to enter the third phase of the repaving project. (See map below for the lane changes.)

Department of Transportation officials had initially planned to make the switch on Wednesday night, but decided to hold off to give the construction crews a break and allow time for the extra lane closure to be made smoothly.

Traffic has slowly been building each commute day through the Interstate 5 construction zone, but so far there have been no huge backups that officials feared could have happened if not enough people stayed off the highway.

But that could change on Friday.

"We are seeing a little bit of building traffic volumes every day on the project on northbound I-5," said DOT spokeswoman Laura Johnson. "We can't have that happening tomorrow."

The contractor hired to repave the road surface and replace expansion joints is ahead of schedule.

The repair project is on track for completion 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 Interstate 90.

On a normal weekday about 126,000 drivers use the stretch of I-5 that is being repaired.

Many commuters started out the week packing Sounder trains and buses, but use of the alternate methods of transportation has been decreasing each day and more people are getting in their cars and heading back to I-5.

Officials are urging drivers to stick to the alternate routes on Friday to avoid huge backups on I-5 heading into Seattle.

For More Information:

Check our online traffic section for continuing coverage of the I-5 construction project, get your questions answered by KOMO traffic reporter Jenni Hogan, and check travel times, live cameras and more:

http://www.komotv.com/traffic