All lanes of Interstate 405 through downtown Renton reopened just before 8 a.m. Sunday, three hours ahead of schedule.

The freeway was closed in both directions starting at 2 a.m. Saturday in order to demolish the old Benson Road bridge over the freeway and do additional work on the freeway, including replacing some worn concrete panels in the freeway surface.

Officials had indicated on Saturday the reopening was somewhat fluid, dependent on work progress and on the weather, which has been hot. The new concrete panels needed to cure before the freeway reopened.

The early reopening is good news for the organizers of the Return to Renton Car Show this morning at the Piazza in downtown Renton. It starts at 11 a.m., following some preliminary organizing before that.

Officials had hoped that about 100,000 vehicles would divert from the I-405 closure area. That seemed to work, as potential 13-mile backups didn’t materialize on I-405 and I-90.

The worst congestion of the weekend was on northbound State Route 167 between Kent and Renton where drivers experienced up to 20-minute delays as traffic backed up south of the closure. Drivers on I-5 also experienced minor delays due to the increased volume from traffic diverting from I-405.

The detours through downtown Renton also caused slow-moving traffic on Saturday.