Bridge Clearance for Semi-Trailers?

[Dave-the-Train]

It just occured to me...

I know that the structure gauge for rail traffic, including Double Stacks, is a little over 20' so that in H0 it's advisable to use 3" clearance over railhead wherever possible BUT... with a view to highway bridges under RR tracks...

What wuld be the "standard " clearance that didn't require "Low Bridge" and similar signs to be posted on the approaches?

Is there a single National Standard or is it State by State?

Do Semitrailer box bodies come built to a standard height with "overheight" specials that are labelled in the same way that RR Bocars are standard or overheight?

TIA

[edo1039]

Most federal hwy(interstates) are an average of 15'. Early bridge structures were much less,anywhere from 9'- 13' depending on where you were in the USA.

[bogp40]

It just occured to me...

I know that the structure gauge for rail traffic, including Double Stacks, is a little over 20' so that in H0 it's advisable to use 3" clearance over railhead wherever possible BUT... with a view to highway bridges under RR tracks...

What wuld be the "standard " clearance that didn't require "Low Bridge" and similar signs to be posted on the approaches?

Is there a single National Standard or is it State by State?

Do Semitrailer box bodies come built to a standard height with "overheight" specials that are labelled in the same way that RR Bocars are standard or overheight?

TIA

Dave,

Are you trying to run the absolute min clearance for this particular division and equipment, or do you plan to have proper clearance for any piece that you may eventually run? The NMRA standards gauge will give you the height requirements for double stacks and autoracks. The only concern is when side clearances have to adjusted on turns.(pilot overhang and inside overhang of long equipment)

[jeffrey-wimberly]

I use to be a truck driver and have passed under many bridges and overpasses. The lowest I've seen that could be cleared by a standard cargo box trailer 13' 6". That's the clearance on a railroad overpass in Leesville, La where the rr track passes over a major highway. I've seen some trucks get caught under it with a few being severely damaged. The biggest percentage of trucks having problems with it are log trucks that have the logs piled too high.

[dti406]

When the Interstate Highway System was initiated the minumum clearance was set at 16'.  Most trailers were then designed with a 13'6" maximum height. Also that was the minimum, many times the clearance was much higher.  Since most trucks were at 13'6" there was no use for the low clearance signs. The signs were mostly required when the clearance got down to about 14'.

What has happened is that as the asphalt overlays were done and the highway departments took the berms and made them traffic lanes sometimes the minimum has dropped down to something under 16'.

Many old railroad overpasses sometimes have a 10'6"  clearance, I remember one of those in Toledo, Ohio and many a truck either removed the top of the truck or got stuck under that one.  

Rick 

 

 

 

[mlehman]

Clearances changed as the interstate network expanded in the 1960s, making the 13'6" clearance the new national standard. Many areas back east had the low 10'6" that was mentioned on certain ruotes, but I can remember 12'6" as being fairly standard on most routes before the interstate. Like many things on the prototype, the era you're modeling makes a difference.

[gear-jammer]

The federal height limit is 13'6", with some western states allowing 14'.  Any overpass/bridge under 16' should be labeled.  Permits and special routing are required for oversize.

Sue

A little Blue Comedy Tour humor.  A truck gets stuck under an overpass.  The trooper comes up to the trucker and asks, " Did you get your truck stuck?", and the trucker says, "No, I was delivering this overpass, and I ran out of gas."

[loathar]

You can buy trucker maps that show bridge clearance for the whole country. 13'6" seems to be pretty common. We built some equipment in Florida that had to be shipped to Montana. We weren't even thinking about bridge clearance at the time. We had to hire an extra low, low boy to make the delivery. Even then, he had to plan a special route to avoid low bridges. That was one $$$$$ mistake.

[NeO6874]

A truck gets stuck under an overpass.  The trooper comes up to the trucker and asks, " Did you get your truck stuck?", and the trucker says, "No, I was delivering this overpass, and I ran out of gas."

 

"...there's your sign..." 

[gear-jammer]

A truck gets stuck under an overpass.  The trooper comes up to the trucker and asks, " Did you get your truck stuck?", and the trucker says, "No, I was delivering this overpass, and I ran out of gas."

 

"...there's your sign..." 

You saw it, too.

[Dave-the-Train]

Your efforts remind me... there's an airfield near Brighton for which a sign says "xxxx international airport -->  height restriction 7'6"".  Now that is low flying!

Thanks for the answers.

Something that occurs to me... what about Grade seperations?

Again, is the a Federal standard for signing low bridges or is it done by State... or even by county?

TIA

[cacole]

There's a one mile stretch of Interstate 10 here in SE Arizona that has never been recognized as part of the federal Interstate highway system because a Union Pacific bridge is only something like 13' 6" clearance and the lanes have no median between them because the bridge is too short.

Union Pacific and the State of Arizona are currently drawing up plans to re-route the rail line so the bridge can be removed and the highway can be rebuilt.  Until that happens, many trucks must take a long detour.

[Anonymous]

Dave, I'll shed a little light on your question.As a general rule ,set your bridges to about 40' tall because almost all wires (electric)must have a minimun clearance of 35'.Poles are taller at all railroad crossings.Hope I helped a little.

[Anonymous]

Dave, everyone is right about the road bridges, 13'6" is for road traffic. sorry about that.

[twcenterprises]

There are some federal rules about signing low bridges, but it boils down to this:

If it's a truck route, statutory clearance is 13-6".  Some states have statutory clearance of 14'.  All truck routes have bridges lower than this MUST post the bridge, and should have (if not must have) sign in advance of the bridge, say at least 1/2 mile to 1 mile.  If the road is truck restricted or truck prohibitied, then advance warning signs are not needed, but the bridge should still be posted for the joker who tries to take a rental truck through.

Many trucks have hit bridges, sometimes the state or county ends up paying for the damages if the trucker can prove the bridge was not properly marked, and the road was not truck restricted.

In HO scale, 13-6" comes out to 1.86" or so, 14' comes out to 1.93".  I would allow 2" for road clearance, this would equal 14-6".

Brad