Motorists in the northwest Valley will be getting some good news and bad news starting this week. Construction gets underway on a heavily traveled interchange.

The good news is that construction crews will start work to expand the traffic exchange linking the Loop 303 and Grand Avenue.

The $46 million project will widen Loop 303 into a six-lane freeway at the interchange and add a new bridge next to the existing Loop 303 bridge over Grand Avenue.

The Arizona Department of Transportation said the project also will remove the last traffic signal still regulating traffic along the 36-mile stretch of Loop 303 between Interstate 17 in north Phoenix and Interstate 10 in Goodyear.

The bad news is the construction is going to take about 18 months. Grand Avenue traffic will be shifted by early January north of Sunrise Boulevard. The speed limit on this section of Grand Avenue will be reduced from 55 to 45 miles per hour.

Construction on the Grand Avenue overpass and two other projects along the 303 is scheduled for completion by summer 2016.