LOS ANGELES — After a weekend freeway shutdown marked by breathless warnings then sighs of relief, it’s back to the regular grind today for Southern California commuters. And for once that’s a good thing.

The construction event that many feared would cause the “Carmageddon” of epic traffic jams cruised calmly to a finish Sunday as Interstate 405 reopened nearly a full day ahead of schedule.

The freeway, undergoing a long-planned and long-publicized closure for a 10-mile span that began Friday night to partially demolish a bridge, was reopened Sunday 17 hours ahead of schedule and with no significant problems.