Big highway bridges, not railroad ones

[OldEastRR]

Looking for a big long road bridge and finding  them scarce in N scale. Not a viaduct, a long span fixed only at both ends. Two lane, with pedestrian walkways. Really not keen on roadizing a RR one.

[pnolan48]

How about a few pics of what you are looking for? Bridge pics are easy to find on the Internet. Are you looking for 200-footers or 600-footers?

[OldEastRR]

Good suggestion. I better think about what it should look like.

[pnolan48]

Are you looking for Cape Cod Canal highway bridges at 635 feet, or the Rio Grande Gorge bridge, the scariest bridge I've ever walked across, the George Washington Bridge, etc?

[Spades]

http://www.ebay.com/itm/N-Scale-15-200-Arch-Bridge-Fully-Assembled-Cement-Grey/152101453393?_trksid=p2047675.c100623.m-1&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20160323102634%26meid%3D074fdf0e03434564a4705e4d0c2f09ce%26pid%3D100623%26rk%3D3%26rkt%3D6%26sd%3D151239698215

and

http://www.ebay.com/itm/N-Scale-Laser-Cut-Concrete-Arch-Bridge-Kit-Our-Original-Design/281951349279?_trksid=p2047675.c100623.m-1&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20160323102634%26meid%3D074fdf0e03434564a4705e4d0c2f09ce%26pid%3D100623%26rk%3D1%26rkt%3D6%26sd%3D151239698215

or with modification. I know you don't want to do that.

http://www.ebay.com/itm/Tomix-N-Scale-3222-Double-Track-Song-Chord-Large-Truss-Iron-Bridge-with-Tracking/182040443657?_trksid=p2047675.c100623.m-1&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20160323102634%26meid%3D074fdf0e03434564a4705e4d0c2f09ce%26pid%3D100623%26rk%3D5%26rkt%3D6%26sd%3D151239698215

[MVW]

That concrete arch bridge is beautiful. Thanks for the reminder on that one. Need to find a home for one of those.

Jim

[thomasjmdavis]

big long road bridge and finding  them scarce in N scale. Not a viaduct, a long span fixed only at both ends

If I understand correctly, the OP is asking for a bridge with a road on it, rather than tracks.  He also asks for no center supports, which leaves out the Rix bridges, which would have been my first thought- since you can buy them in 50 or 150 foot "modules" and assemble any bridge length you want.

Questions for Old East would be -
How long is "real long"?
Over water or over another highway, or railroad, or canyon?
What time period?

Would note that a double track railroad bridge could be kitbashed easily enough, or if it is long enough and still available, Plastruct has (or used to, not sure) a "kit" for a truss bridge, that since it consisted primarily of a lot of structural shapes, would be easy to convert to highway use, since railroad particular parts are not cast in.

[SecretWeapon]

I made this one. Used a Kato bridge & masonite.

[SecretWeapon]

Here's the full view of the bridge.

[wazzou]

Here's the full view of the bridge.

Nice.  It looks like a display shelf for Trainworx trucks or a big traffic jam.   

[wm3798]

Well.... Bridges, like all things, and maybe more than some things, are subject to the laws of physics.  A long span without intermediate supports will require some sort of long truss, probably cantilevered to maximize the span between the piers, but there will still be piers.  Even a suspension bridge requires towers to carry the cables.  A long arch, such as New River Gorge in West Virginia, https://www.google.com/search?q=new+river+gorge+bridge&biw=1920&bih=971&tbm=isch&imgil=60KDG_Orn1UFpM%253A%253BHonEgNy3qJivJM%253Bhttps%25253A%25252F%25252Fen.wikipedia.org%25252Fwiki%25252FNew_River_Gorge_Bridge&source=iu&pf=m&fir=60KDG_Orn1UFpM%253A%252CHonEgNy3qJivJM%252C_&usg=__jcLqx_GXwwQmBO6EYzeV-kAnSGk%3D&ved=0ahUKEwiu6P-4xYfOAhVFKh4KHQayDB8QyjcISg&ei=plCSV679G8XUeIbksvgB#imgrc=60KDG_Orn1UFpM%3A

Might be what you're looking for.  Although, a major structure like this might, for economic purposes, be more than two lanes. 
Here's my well-worn article about bridges on my old layout.  It pertains mostly to railroad bridges, but there's some discussion of bridge basics which would pertain to roadways as well. 
http://www.wmrywesternlines.net/st_bridges.php


This is the big viaduct I built to represent US 48 (now I-68) through Cumberland.  I think the spans were about 180 scale feet.  I used four or five piers to carry it across the city scape, the WM tracks, and Wills Creek.

I guess a key question would be how long of a span are you looking for, and what kind of terrain are you spanning?



N scale railway bridges can be easily adapted to highway use, but to make it as realistic as possible, give us a little more information about your application...

Lee

[peteski]

I made this one. Used a Kato bridge & masonite.

The photo does not seem to show any sort of support where the Kato truss bridge ends and the concrete bridge begins. Is that in fact the case? 

[jmlaboda]

Seems to me the first place to look is Rix Products, which manufactures highway bridges...

http://www.rixproducts.com/6280103.htm

[wm3798]

The photo does not seem to show any sort of support where the Kato truss bridge ends and the concrete bridge begins. Is that in fact the case?

Again with those pesky laws of physics!

[Pomperaugrr]

Without knowing the era, terrain, height or length of the bridge you need, I would also recommend the RIX Bridges.  I used the railings, but scratchbuilt the road and columns and abutments with styrene to make them look more eastern.



Column base with spalling concrete and rebar showing. Prior to scenery...


Rix also makes modern versions.

Eric