CHICAGO (CBS) — “Lucky.”

That’s how a highly regarded civil engineer described Monday’s Lake Shore Drive bridge.

He spoke to CBS 2 Investigator Brad Edwards.

“In this case, it just so happened that someone caught it at the right time,” said P.S. Sriraj of the University of Illinois at Chicago.

According to Sriraj, a leading voice on infrastructure, Illinois has the third largest inventory of bridges in the country.

“16 percent of those bridges are deemed structurally deficient,” Sriraj said.

That’s nearly one in five.

“And that’s an alarming number considering the amount traffic that Illinois gets,” he added.

The bridge in question passed its latest inspection in 2017 by the Chicago Department of Transportation. But there were problems according to a state document. There were minor deterioration and cracks which may have lead to the problems discovered on Monday.

IDOT will pony out 2.6 billion over the next six years for bridge maintenance and improvements but its own estimates, 10 billion dollars are needed.

That’s a 7.4 billion dollar underfunding.

Sriraj examined pictures of the bridge and said it looks like the break was caused by a support column shift.

Bigger picture: Federal records show of the 1,700 bridges in Cook County, there were 1,200 with worse inspections than the one on Lake Shore Drive.