i checked out this book from my library about lionel trains and found a lot of cool things inside i want to share with you guys
but i also have questions
1 is the lift bridge from the postwar period available for sale
2 could i use the bridge as an elevator and move a train from one level of track to another
1) to the best of my knowledge (memory may be foggy, but I recall reading about it years ago), there was only one prototype produced of the PW bridge, so it's effectively not ever available for sale. However, the more recent lift bridge Lionel produced was closer to that style. It's black and made mostly of metal similar to the PW prototype. It is seen for sale regularly. It is not as good in terms of all engines and cars clearing it though (small opening) as the larger bridge you show in the photo. I had problems even with a small caboose not clearing with it's smokestack installed.
2) No. the bridge would not survive more than maybe one or a handful of attempts at raising it with an engine on the span. It is meant to move the span only. (and as Adriatic said, the bridge structure itself would be in the way.)
Ive seem some nice metal liftbridges at shows to save ducking under. Not for sale that I know of.????A vertical transfer table! 
I think it would make for a great long term project with a huge wow factor if used with multiple levels. I think two levels are going to need a bi-level span to use both levels for running unless its strictly used as an elevator on a siding , or with a bypass on each level. But then youre back to duck under possibly.
Dont stop dreamin' 
There was (is?) a company called AAA Turntables that makes very sturdy gigantic lift bridges for this purpose. (they also make turntables and coal accessories) These are many times larger than the standard Lionel bridges (you could not fit most in a car or even small SUV), but they are meant for raising so people can walk under. They brought a few examples to York over the years. I think if you want one, they are made to order (they are also not cheap, probably several thousand dollars a piece, but most likely very much worth it if you have a need/desire for a functional lift bridge that you can walk under).
Somewhere a while back there was a magazine article about using something like a garage door opener motor drive to raise and lower a long section of track to allow storage tracks to be driven onto the layout. It was quite elaborate and needed sturdy tracks to run on similar to a garage door if I recall. Something similar could probably be used to change between levels, but it's going to be a lot more work than it's probably worth for most people.
-Dave
