> Michael Healy, a BART historian and the former BART Director of Public Affairs, believes the use of the broad gauge “goes back to when BART was planned to go across the lower deck of the Golden Gate Bridge,” he told BART recently.
> “High winds coming through the gate would have required more stability for the aluminum-shelled cars. Thus, the wide gauge, as I recall,” he said.
Why that particular gauge (five-feet-six-inches) and not the more widely-used standard ( four-feet-and-eight-and-a-half inches)?
> The pamphlet does not specify why only the wide gauge of five-feet-six inches was tested and not others. One possibility is that the broad gauge was among the more widely used gauges in other countries. Another theory is that complex calculations were required, thus limiting alternatives that could be practically evaluated at the time.