OLYMPIA – Washington state transportation commissioners have approved toll amounts for the Highway 99 tunnel in Seattle.

The tolls will range from $1 during slow traffic hours to $2.25 during rush-hour traffic on weekday afternoons.

The tolls will increase by 3 percent every three years. The first increase is set for 2022.

Toll revenue will fund ongoing maintenance, operations and safety systems as well as pay down the $200 million in construction costs.

Until tolling equipment is installed, trips will be free on the nearly 2-mile tunnel from Sodo to South Lake Union when it opens in January.