BOSTON -- Team 5 Investigates has uncovered new information about the condition of a bridge in such disrepair a large piece of concrete fell onto a driver Monday.

The Cambridge Street bridge in Allston was labeled structurally deficient in 2007 after problems with concrete were detected.

The state took steps to repair the concrete, but still a large piece fell onto Margaret Garvey of Marlborough as she was driving on the Mass Pike.

"Before I knew it, all of the rocks -- tons of rock -- had come through my windshield and through my sunroof, which was open and landed on me," said Garvey.

Garvey was lucky to escape with minor injuries and was relieved her young son was not in the car.

"I pray they continue to do repair work," said Garvey. "I'm very lucky."

Crews were out overnight making repairs, but engineering experts tell Team 5 Investigates temporary fixes are not enough.

"They're going to be spending $3 billion to repair structurally deficient bridges over a period of eight years," said Joe Durant, president of the Massachusetts Organization of State Engineers and Scientists. "That will only repair half the structurally deficient bridges so more has to be done in the future."

In fact, Team 5 has learned approximately 600 of the 5,500 bridges in the state are structurally deficient.

Incoming Transportation Secretary Jeffrey Mullan called the Cambridge Street bridge incident unacceptable. But he acknowledged the state does not have the resources to make all the necessary repairs.

"We've got unprecedented progress being made towards hundreds of our bridges, but it's a constant battle to keep up with the aging infrastructure our commonwealth has," he said.

The Massachusetts Transportation Finance Commission said Massachusetts needs $1 billion a year to keep up with roadway and bridge repair.