I recall from the time BART was under design that some apprehension was expressed about lateral wind forces on the Golden Gate Bridge (which turned out to be irrelevant for other reasons). Certainly the planners realized that all of their prospective passengers already had a way of getting to work in an air-conditioned vehicle with comfortable seats--that's how they were getting to work as it was. What spurred a desire for BART was that these vehicles spent more time standing in traffic than moving, at least during rush hours. The planners felt they had to offer something better than a plain box with benches, since riders could revert to using their own cars in a heartbeat, traffic jams notwithstanding, and the more generous loading gauge made wider carbodies possible. (An interesting parallel here with the construction of the Metropolitan Railway in London in 1863; the target ridership at the time was fairly prosperous residents who used hansom cabs and their own carriages, and if they were offered wooden benches they'd take one ride and never come back. Thus equipment on the London Underground has traditionally had comfortably upholstered seats and armrests ever since.) It seems that the interiors of the new BART cars are not going to measure up to the comfort of the originals.