Mostly, those structural changes have already been made that would make any rapid transit technology possible on the bridge. That modification, made long since putting trains on the the bridge was first questioned by civil engineers, involved replacing of the previous roadway deck structure with a much lighter more modern one.

Another mis-impression that should be "Daylighted" is the idea that heavy rail transit vehicles are actually heavier than so-called light rail cars. Generally, they are not! At 68,000 lbs per car (fully loaded), BART cars are in fact lighter than most so-called light rail vehicles. Actually, the term "Light Rail" refers only to the construction standards of the trackage, which is generally much flimsier, and allows many more compromises such as at grade highway crossings. (the downside of lighter construction is higher maintenance costs and higher accident rates)

As Mike Pechner pointed out on an earlier related thread, the bridge structure has already been lightened by 18,000 tons. Therefore, it -IS- doable. And there surely is room enough for one track (BART would need only 12ft) between the bracing on the lower deck; and it would not add back anywhere near the 18,000 tons already removed. Same with any light rail or even the much maligned DMU's.

OPB