Unless they are the Golden Gate, the Brooklyn or span the River Seine, bridges don’t get a whole lot of attention, and the bridges that got their 15 minutes of fame on Friday figure to be absorbed into the urban landscape pretty quickly.

That said, the 11th Street freeway bridges over the Anacostia are a big deal.

At a cost of $300 million, they are the biggest project ever undertaken by the District Department of Transportation.

Also a big deal: They were finished ahead of schedule.

“Just two years after construction began, we have already arrived at this important juncture,” Mayor Vincent C. Gray (D) said at Friday’s ribbon cutting. “This $300 million project — the largest DDOT has ever undertaken — is ahead of schedule and represents a giant step forward for our transportation system. Critical for connecting one city across the Anacostia River, these new spans will serve our residents, workers and visitors for decades to come.”

The two bridges connect Interstate 295 with the Anacostia Freeway. A third bridge that will carry cars, bikes and pedestrians between Anacostia and Capitol Hill is to be completed by next summer.

Construction of the three-bridge cluster began in December 2009. The bridges are projected to carry 180,000 vehicles a day within 20 years. They replace a pair of bridges that were judged functionally deficient and structurally obsolete.

This weekend, inbound traffic will be shifted to the new freeway bridge, with work expected to be finished by the time rush hour begins Monday. The outbound freeway bridge is tentatively scheduled to open next week.