Durham, N.C. - Last week's tunnel ceiling collapse in Boston that killed a motorist has taught us more about the "Big Dig" ceiling system than all the years of apparently successful operation, says a Duke University civil engineer and author of "Success through Failure: The Paradox of Design."

"For years the ceiling design appeared to be successful, in that cars and trucks drove through the tunnels without incident," said Henry Petroski, Aleksandar S. Vesic Professor of Civil and Environmental Engineering at Duke's Pratt School of Engineering. "But the fact that no ceiling panels had fallen was not really proof that the design was flawless. The 'success' only masked latent flaws in the system."

The failure now provides an opportunity for design improvements that might not otherwise have been made, said Petroski, the author of 13 books about bridges, pencils, paperclips, books and bookshelves, engineering errors and more.

The Big Dig incident is the most recent of many historical cases to highlight the paradoxical role of failure in successful engineering and design, which is the focus of "Success through Failure" (Princeton University Press, February 2006). The sinking of the Titanic is another infamous example, he said.

"Had the Titanic not had the bad luck of striking the iceberg, it might have had a successful voyage and continued to cross the ocean without incident for years," said Petroski, a member of the National Academy of Engineering and chair of the American Society of Civil Engineers' History and Heritage Committee.

"It would have been hailed as a success and provided a model for other steamship designers to follow. Other ships designed after the Titanic model would likely have had all its flaws and so also have been vulnerable to a collision with an iceberg. This is the way it is with success-based engineering and design generally."