What's the deal with the "D" on a "wide load" sign?

April 20, 2007 9:16 PM

A "wide load" vehicle on the highway seems to always have a sign on the back to indicate that it's a "wide load", but the sign doesn't say "wide load". Instead, it has the letter "D" in the middle of it, and red/white vertical bars. Why a "D"? What does the "D" stand for? Why not just have the sign say "WIDE LOAD"? I'm in Canada, if this is something that'd be different in other countries.
posted by gwenzel to travel & transportation (11 comments total)

The "why" seems to be because that's what the regulations say. I have no idea what the D actually stands for. And yes this does seem to be a Canadian thing, I've never seen this before in the States.
posted by Rhomboid at 9:29 PM on April 20, 2007

In the States, they say WIDE LOAD.
posted by disillusioned at 9:30 PM on April 20, 2007

"D" stands for dang, that's a wide load!

Actually, it stands for "Overdimensional." LOL Canadians.
posted by found missing at 9:57 PM on April 20, 2007

The "why" seems to be because that's what the regulations say.

Actually, those regulations say that "a sign that says a sign visible for a distance of at least 150 m bearing the words "OVERSIZE LOAD" in black letters at least 200 mm high with lines forming the letters at least 30 mm wide on a yellow background, or a "D" sign as illustrated below."

Given those regulations, the D probably became popular as it is totally unambiguous. You buy a conforming D, and you're always good to go, whereas the OVERSIZE LOAD sign has a clause ("visible for a distance of at least 150m") that could be abused by unscrupulous police, or by an attorney in the case of an accident.
posted by Tacos Are Pretty Great at 10:12 PM on April 20, 2007

Rhomboid: "The "why" seems to be because that's what the regulations say. I have no idea what the D actually stands for. And yes this does seem to be a Canadian thing, I've never seen this before in the States."

Just a little nit-pick: That link is for the province of Ontario -- ministries of transport are under provincial/territorial purview. I expect these rules are probably more or less across the country, but they are individual laws and in many cases they differ.
posted by loiseau at 10:58 PM on April 20, 2007

I realize that is a link to the Ontario regs but when googling I found hits with the same wording in other provinces and I really didn't feel like typing this paragraph to explain that.
posted by Rhomboid at 1:41 AM on April 21, 2007

Idle speculation, but I wonder if it's part of the definition of truck types. I've heard of A train trucks--ones with single, normal trailers--and B train trucks--ones with double trailers, usually one longer than the other. Perhaps D is a designation for wider trailers/loads than usual?

Of course, now, I'm left idly speculating about what C might mean.
posted by jacquilynne at 11:22 AM on April 21, 2007

No, "D" stands for "overdimensional", no need for further speculation. They use the D from dimensional to abbreviate the word.
posted by found missing at 11:48 AM on April 21, 2007

jacquilynne both A and B trains are composed of a tractor and two or more semi trailers.

Int he case of an A train the first trailer is hooked to the 5th wheel of the tractor. The second trailer is hooked to a little trailer essentially consisting of only a 5th wheel called a Dolly. The dolly is pulled by the first trailer using a pintle connection.

This is in contrast to a B Train in which the first trailer has an integral 5th wheel at the rear which pulls the second trailer.
posted by Mitheral at 12:43 PM on April 21, 2007

the D probably became popular as it is totally unambiguous.

This thread would not exist if D were not ambiguous.
posted by Kirth Gerson at 1:50 PM on April 21, 2007

The D is unambiguous (no one thinks it's an O or Q for example) it just isn't intuitive.
posted by Mitheral at 4:31 PM on April 22, 2007