SEATTLE -- Thousands of people turned out Saturday for festivities celebrating the opening of the new State Route 520 floating bridge across Lake Washington -- so many that the state Department of Transportation declared the event "at capacity" and halted buses that had been expected to shuttle additional people to the structure.

Gov. Jay Inslee cut an orange ribbon Saturday at the middle of the 1.5-mile-long span to commemorate the completion of work, more than 12,000 people participated in a 10K fun run, and a representative of Guinness World Records presented a certificate designating it the world's longest floating bridge -- at 7,708 feet, it's about 130 feet longer than the old one.

"This is what it's all about -- seeing years of public engagement, planning, design and construction all come to fruition," said Roger Millar, acting transportation secretary. "This grand bridge is going to serve our region well for a long, long time."

The six-lane bridge, which replaces a four-lane version built in 1963, doesn't fully open to car traffic until later this month -- April 11 for westbound traffic and April 25 for both directions. The state says it features heavier, stronger pontoons and anchors that allow the structure to withstand stronger winds and waves; a bus and carpool lane in each direction; a 14-foot-wide bike and pedestrian path; and system to collect and treat storm water, which will improve water quality in Lake Washington.

The old bridge is expected to be dismantled by the end of the year.

On Saturday, the masses strolled along the car-free pavement and enjoyed views of the lake and the mountains on a beautiful spring day. But it was so crowded that some complained about an hour or more for shuttles to make their way off the bridge, and the lines at the food trucks were formidable.

The state DOT communicated with frustrated bridge-goers by Twitter, sending messages such as "event is currently at capacity. We're working to move people on the bridge off & are halting inbound bus loads for AT LEAST an hour," and, "Water is on its way to folks waiting for shuttles .... Thank you for your patience."

Apparently everyone wanted to see the world's longest floating bridge, sorry we couldn't accommodate more. https://t.co/Ke0kweU6YQ — Washington State DOT (@wsdot) April 2, 2016

The celebration also featured interactive exhibits for children focusing on science, technology, engineering and math.

Festivities were scheduled to continue Sunday, with 7,000 bicyclists joining a 20-mile ride across the bridge and through downtown Seattle streets that will be closed to car traffic.

-- The Associated Press