From TFA: “The pamphlet does not specify why only the wide gauge of five-feet-six inches was tested and not others.”

Standard gauge was ubiquitous in the US at the time, and this engineering firm didn’t even evaluate it in their report, despite the fact that the original BART plans called for standard gauge. Stability of standard gauge has since been proven to be a complete non-issue.

If you read more about the history of BART, everything about it was NIH. They thought they were going to design some new space-age standard and usher in a new era of public transportation.