The Gordie Howe Bridge, connecting Windsor and Detroit, ultimately cost $6.4 billion dollars—$700 million more than anticipated—and its opening was pushed back from 2024 to 2026 amid political tensions. Credit: Unsplash/CC0 Public Domain

Nine out of 10 major transportation projects go over their initial budget . This isn't always because of incompetence.

In many cases, a specific dollar figure for the project is announced too early, when there are still a lot of uncertain variables. But shaky assumptions soon become public promises, after which the cost overrun—though predictable—becomes a scandal. People look for a simple explanation or sometimes a scapegoat.

In reality, cost overruns can stem from a wide variety of causes. Some result from external factors, such as rising costs of materials, labor shortages, changing regulations or an economic downturn.…