Why does BART use wider, non-standard guage rails?

Nearly every other rail system in the US uses 4′ 8.5″ rails, why does BART use 5’6″ rails? This seems a negative as it means it can’t share tracks on any other railroads in the US, can’t be used to ship freight or use low cost off-the-shelf rail vehicle or maintenance equipment – everything, requires custom designed equipment to maintain and operate?

A: It is unclear if there is a “rational answer” to this question.

This question has been posed directly to a BART General Manager who said he did not know why.

HOWEVER, what we do know from engineering principles what the reasons for the extra width DO NOT include the following urban legends:

  • It is not due to speed. Taller trains travel on conventional gauge rails travel at 200+ mph in Europe and Japan. Caltrain runs just as fast as BART–even though it has much taller cars (with twice the seating)
  • It is not to resist train roll-over in high winds, such as crossing the Golden Gate Bridge.

An contemporaneous account of the reasons is given in the BARTD gets is first test track car. Western Railroader June 1965 Vol 2806 Issue 305: “Clara (the test car) arrived at Concord from Sacramento in a special Sacramento Northern train. She rode on a WP flat car instead of on the rails since she has a 5′ 6″ gauge, nearly a foot wide thant the 4″ 8.5″ standard gaguge used by most existing transit systems and all the nations railroads. Parsons Brinckerhoff- Tudor Bechtel, the districts consulting engineers, said that exhaustive studies show the wide gauge provides great stability and smoother riding qualities for the rapid transit trains.”

FAQ courtesy of Alan Hirsch