The reason some of us despise much of BART's design/execution is that in nearly every case they made poor to horrendous mistakes. The incompatible guage was claimed to be necessary for high speed trains in the BAY Area because of high winds. Of course, at the time the rapid transit speed record was held by CTA (in the Windy City) with hotrodded PCCs on4'8 1/2" tracks. In fact, there is good circumstantial evidence that the decision was driven by the connection of the Bechtel family to the SP who wanted to get rid of what we now call Caltrain. (S.D.Bechtel Sr. was chair of the SP Co and Jr. a director when Bechtyel was part of the design/oversight consortium which brought design ideas to the then rubber stamp board). It was the consortium which brought us the "Buck Rogers" wedge front design--the cost alone of having to switch a train into a yard to add/subtract cars twice a day was a total waste.
Choosing Westinghouse for the train control system (something they had never built) was another costly mistake. (BTW the CPUs were re-decaled GE machines--from a division long since sold off to Honeywell)
In sum, it was a typical DOD procurement--poor RFPs generating poor contracts--late and non-performing products requiring millions in retrofits. And, given the delays from skiddoo (Bombardier's original business) we will have inadequate service for several years to come.

Other than that a moderately decent subway by 1950 standards.