In a pit thread there was a post to Warning signs of the road:
http://homepages.cwi.nl/~dik/english/traffic/signs/Aa.html
At the bottom of the page, we have A97a: A worded sign as used in the UK
It consists of the word Ford inside a white triangle with a red edge.
Maybe a warning to Ford Prefects to stay off the road? 
What is that sign for?
My educated guess is that it warns of a shallow water crossing in the road ahead.
Dead vehicles on the road. 
More likely a stream crossing at “A shallow place in a body of water, such as a river, where one can cross by walking or riding on an animal or in a vehicle.” As Frodo found out on the road to Rivendell, unmarked fords can be hazardous.
My best guess: It has nothing to do with Ford Motor Co., American or British. Rather:
The road (lane) crosses a shallow stream by a ford rather than a bridge or culvert. That is, you drive through the shallow water across the stream.
Yep, that sounds about right.
This is the first time I’ve heard of that definition myself.
Aha, thanks guys! With that context I get that also in Canada they call it that way:
http://www.exploringthenorth.com/ottawa/ehlco.html
Google was getting me lost with Ford car items in the UK.
Climb every mountain…ford every stream…
It’s actually a sign warning “Illuminati Ahead”. (The “n”, naturally, is invisible).
Here’s one in a village near me.
They are often followed by a “Now Try Your Brakes” sign the far side. The one near my parents is now dry more often than not but the sign is permanent;
Ok, question answered, but now I’ve another that involves that same spot.
How do they construct it?
I’d imagine that it would be tough to get a good road surface by paving under standing (or flowing, which I’d imagine would be worse) water???
-Butler
“Why you need-a a horse when you have-a a ford?”
Well in the more remote areas they don’t always, it may just be the stony stream bed but in a lot of places the presence of water is seasonal.
Well, sometimes it’s only a ford in very wet weather, but mostly they don’t pave it at all. Look at the photo linked in GorillaMan’s post: just a track, really. Any road worth paving would also be worth building a bridge for.
These fords are usually on very small roads and so they can be made of stone slabs simply laid down.
Lots of fords are dry for most of the year, only becoming water routes during winter or heavy periods of rain, and there is enough time to put down a normal concrete layer.
Normal ashphalt is useless as it just breaks down.
Many fords will have a footbridge next to them for pedestrians.
Now you’ve got me visualizing that scene in FOTR with a big “FORD AHEAD” triangle sign alongside the road! 
Concrete will set under water. How do you think they build dams?
Somewhere in Montgomery County, PA, in the general vicinity of Bryn Mawr and Haverford, there is a small paved road that fords a stream. I believe it is paved in concrete.
They’re quite common around here. Normally, they are just constructed of very, very thick concrete. They seem to withstand the decades.
On a side note, the local signs say “DIP”. One New Zealand tourist, traveling at high speed late at night in his hire car saw this sign and dutifully dipped his headlights. He reckons he cleared the entire thing airborne, Dukes of Hazzard style. Didn’t do his suspension (or his nerves) much good, he said.
Yep. The one in question is just the gravel-covered bed of the stream. This is often the case - because the river was forded at the shallowest and least muddy place to start with.
And here’s one near me:
http://www.nwkfhs.org.uk/EYNSFORD.JPG
(How do you do that blue linky thing?)
