Tolling of the southbound Highway 99 tunnel under downtown Seattle begins at 5 a.m. Saturday. Tolls on the northbound direction will start at 8 a.m. Saturday when those lanes reopen after being closed overnight for routine maintenance.

Tolls are charged each direction and vary by time of day, from $1 on nights and weekends, to a peak of $2.25 on weekday afternoons.

The tunnel has no toll booths or cash payments. Tolls are collected via electronic cameras and sensors that record a windshield-mounted, state-issued Good To Go transponder that links to a driver’s prepaid debit account.

The state also offers a “Pay by Plate” alternative, to register a license-plate number instead of using a transponder, at a 25-cent surcharge per trip.

If you don’t have a Good To Go account you will be billed by mail, plus a processing surcharge of $2 per trip.