I need to build two highway bridges over the tracks on my layout; one will traverse at least 4 tracks (as many as 6). I have lots of reference on building railroad overpasses but not highway. I need some ideas on not only the road structure but the bridge itself. These will be at least two lane paved highways, not country roads. Pictures, suggestions, instructions will be appreciated.
I know you will hate this, but I will answer your question with a question. What period are you asking about?
If it is now I would do pre-stressed concrete, but if it goes back to the good old days then something else might be more appropriate.
I'd first look at what's in the Rix product line. They have a couple of versions of highway bridges. Other than that they are not too hard to scratchbuild from styrene. I built a couple of freeway style overpasses a few years ago which look the part. From my own observation (don't have the pics here to show) most overpasses would have piers cast in-situ opon which precast beams are laid followed by a concrete topping to form the road deck.
Back in the '50s and early '60s (if my childhood memories are correct) a lot of the highway bridges over streams and rivers (at least in the rural areas of Virginia, West VA, Penn) were steel through trusses very similar to railroad bridges. Quite a few were one lane, too.
my experiences, your choices
The era I am modeling is late 60's-mid-70's so the bridge could conceivably have been built anywhere from the late 30's up until that time. I am thinking concrete structures.
I had a look at what the other guys suggested. Walthers Part # 628-103 from Rix looks nice. However, it's your choice.
Hey, #628-102 is on sale! Three @ $9.98 ea. works out cheaper than One @ $34.95. Might be short one pier?
Look at these offerings from Walthers
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Here in Washingtion and Oregon, some of the highway bridges are STILL steel bridges looking very similar to railroad bridges, just with concrete center and rails on sides going thru the steel frame....Here are some pictures..
Hope this helps...
I have the Rix concrete bridge and I like it. You can add as many sections as you like and it's adjustable vertically by cutting the round columns..
this is a section in the foreground..
The instructions say that the support columns are normally place in (and they tell you the position) but then they say you can move them around a bit to clear obstructions below if needed.
As you can see, mine isn't completed and it may be a while before it is......, I've gotten off on other projects right now.