Trestle or Viaduct?

[The Butler]

After watching an episode of "Trains and Locomotives," I began wondering what the difference was between a bridge, a trestle, and a viaduct.  In the glossary of common terms found on this site, I learned only a bridge crosses water.  In the show I watched, both trestles and viaducts were made of metal (steel?).  How is it determined which is which?

[Erie Lackawanna]

I belive that a trestle, by definition, has vertical support throughout the span (essentially, legs everywhere).  Thus, the old wood and steel bridges that looked like something put together with an erector set are trestles.

I also think that the term trestle gets used mistakenly a lot when refering to bridges that are really viaducts (or bridges).

Of course, I could be wrong.

[The Butler]

Can a viaduct be a bridge?

 

[Erie Lackawanna]

Again, people will call things whatever they call them, but a viaduct spans the depression created by a valley, while  bridge generally goes over something smaller (like a river or a road).  That being said, some rivers are wider than some valleys, and some viaducts go over rivers too, and there are a lot of bridges that have official names that include the word viaduct... so it's not a clear answer.

To me, based on the definition... a viaduct is over a valley, unless it has little horizontal support and thus, is made up of a cluster of legs, in which case it's a trestle... and everything else is a bridge... but it's still ambigous.

[RABEL]

Can a viaduct be a bridge?

 

A Viaduct by definition is a long elevated  roadway, A bridge is a short roadway over a gap

or depression. It would seem a Viaduct may contain Bridges.

[CSSHEGEWISCH]

RABEL's definition is probably about the best and keeps the fudge factor in mind.  Using that definition, a trestle could be classified either way.

[The Butler]

Thanks for the info.

My parents grew up in Chicago where every railroad bridge over a street is a "viaduct."

I was always under the impression trestles were wooden.  I never thought they could be steel.

 

 

[Erie Lackawanna]

The Atlantic Avenue Viaduct in Brooklyn NY, by the way, is a very long steel structure, with legs at almost every ten/twenty feet and no valley anywhere near it.

[selector]

Webster's New World Dictionary describes a viaduct as a series of short concrete or masonary spans supported by piers or pylons meant to traverse a gorge or a valley.  A secondary description is of any railroad bridge.

My own mental image of a viaduct is of concrete arched spans supported on piers across an expanse, and usually a road or a water course runs atop it.  However, I have also seen images of long, high, "viaducts", such as the huge one near Lethbridge, AB on the CPR line, which I would say was a steel trestle.

A trestle has battened stilt-like posts or bents to support wooden or steel spans.  So, as much as there is a lot of room for area and industrial culture-specific use and cross-use, I will hold to a viaduct being something like a longish stone/masonary arch or pier-supported bridge comprising at least two spans, and a trestle being more supported by battened posts/bents, with the entire structure either wood or metal.

-Crandell

[ChuckCobleigh]

Why a duck?  Why a no chicken?

------Chico Marx, The Cocoanuts, 1929. 

[Murphy Siding]

     It might depend on where you live.  Around here, a viaduct goes over a road or rail line.  A trestle goes over water-like a bridge, except with a lot of poles/posts for support.

[RABEL]

My parents grew up in Chicago where every railroad bridge over a street is a "viaduct."

Chicago is an exception to the "rule" , railroad Bridges pass over Viaducts.

[The Butler]

My parents grew up in Chicago where every railroad bridge over a street is a "viaduct."

Chicago is an exception to the "rule" , railroad Bridges pass over Viaducts.

Chicago has many exceptions to all "rules!"    You gotta problem wid dat?

M.S.- If I remember right, the show was about a UP line in the Pacific Northwest.  They showed trains on all three.

[al-in-chgo]

Thanks for the info.

My parents grew up in Chicago where every railroad bridge over a street is a "viaduct."