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What does the label "H "triangle" D" on the back of a trailer mean?

by ash
(detroit, mi)

I am very interested in trucking typography, signage, and symbols. I often see a label on the back of a semi's trailer that will read an uppercase H, followed by a triangle, then an uppercase D. Could you please tell me what this means?

Comments for What does the label "H "triangle" D" on the back of a trailer mean?

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Nov 16, 2025
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Curious
by: Anonymous

It feel like refers to a secret organization that can't be googled because the symbol does not translate I've been wondering about this for ever

May 06, 2018
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Heavy duty lol NEW
by: Anonymous

Haddad.

Apr 16, 2014
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Triangle meaning NEW
by: Ima Trucker

I knew the triangle had to have some significance, so I did some digging. The minimum standards for a heavy duty trailer were a group effort among the "Big Three" automakers, so they decided to adopt the "Triangle". (Big Three) = (Triangle)

Apr 16, 2014
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H "triangle" D trailer NEW
by: Ima Trucker

It means that the trailer has been inspected and certified as being heavy duty to the standards set forth by the auto industry. The trailer must have a minimum number of steel support beams under the wooden floor of the trailer so that a forklift will not bust through (yes this happens). The triangle doesn't literally have any meaning, it's just to easily identify a heavy duty trailer at a glance.

Sep 23, 2013
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h^d
by: Anonymous

I work for Chrysler LLC and several of our fork trucks have this same marking. No one I have spoke to seems to know what this signage means.

Aug 21, 2013
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It is not a conventional HazMat placard
by: Anonymous

I've seen this too. A hazmat placard is diamond shaped and appears on all four sides of the trailer.

The H ^ D appears on the rear of the trailer. The triangle is completely shaded in and I have no idea what it means

@ThisTruckTweets

Nov 24, 2010
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Uhm...
by: Anonymous

"H" usually means 'heavy', but not sure about the other. found this though, you may be interested

http://www.containerhandbuch.de/chb_e/index.html

Oct 10, 2010
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What does the label "H "triangle" D" on the back of a trailer mean?
by: Dennis Shipman

Sounds like a hazardous material placard. Without actually seeing it, it is difficult to figure out what its warning you about. That is what these signs do warn other drivers, police, fire, and first responders that the tank, van or container in question contains a hazardous material enabling them to respond according.

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