I know what this indicates to me…
Do you ■■?
Some drivers look at you as if your an alien…! if you give the thumbs down signal…
I do give a thumbs down if i can alert oncoming trucks of certain situations…!!
Thought us drivers were supposed to look out for each other ■■? or is evryone in such a rush these days ■■? not to give 2 hoots ■■?
I find that the French are best for giving warnings like that, cars and truck drivers warn everyone with a flash of the lights and a thumb wave
I give a repeated headlight flash and a “thumbs down” for a speed trap (Or at least, I would do if it wasn’t illegal 
) and I do a downward waving of the hand to warn of a vehicle broken down in a dangerous position, such as just after a blind bend.
Like you, I’m amazed at how many truckers ignore this.
Harry Monk:
Like you, I’m amazed at how many truckers ignore this.
And I’ve seen some return the gesture by giving either the coffee bean shake or the one fingered salute, makes you kinda hope they get caught after all when they do that. 
Yes, I know what it means - it’s a masonic wave to fellow truckers - it certainly isn’t a warning of a scamera cos that could be illegal
and I’ve noticed truckers ignoring it too, although some might just have noticed it too late to wave thanks - (guilty m’lud)
well quite obviously it means “slow down” as there is some kind of problem ahead be it police, stationary traffic, accident, whatever. Back off!
I used to flash trucks on the m/way that were approaching stationary traffic, but with todays powerful brakes, use of hazard warning lights, etc. etc. I don’t bother anymore. (+ because some used to just flash & wave back 
)
Travelling up the A9 on Saturday p.m.,I was flashed by a s/bound truck. Obviously a problem ahead,but the accompanying hand signal had me totally baffled.Both hands were off the wheel 
,palms up to the screen with fingers out-spread.
Still trying to work that one out. 10 mph? 10 miles to problem? Or “Look,no hands” 
. About 15 mins later,came across the talivan.I assume that is what the driver was warning me about,but why such a hand signal and so far away from the vans location?
Highlander:
Travelling up the A9 on Saturday p.m.,I was flashed by a s/bound truck. Obviously a problem ahead,but the accompanying hand signal had me totally baffled.Both hands were off the wheel
Still trying to work that one out. 10 mph? 10 miles to problem? Or “Look,no hands”
Perhaps it was your estimated time of arrival to the camera based upon the speed you were doing, current road conditions…and the sheer look of lunacy in your eyes
Seriously, will always flash at fellow drivers when I “think” I see someone I know, but only for a couple of miles, beyond that its pointless
years ago,it was tacho card up to the windscreen.
its impossible to let the driver on the other side of the road know the exact problem up ahead,
at least they know there was a problem up ahead
long live cb.
it is the best for info.
now if we could only get sat navs that shows us where vosa are hanging around as well as the speed cams
the menace of the driver.
they take pleasure in prosecuting.i dont believe there is an honest vosa employee.,they just want to ruin peoples days.
they do make me sick.
even when you try to operate right and i do,they still nitpick.
they are the low of the low.
greg50:
now if we could only get sat navs that shows us where vosa are hanging around as well as the speed cams
.
There is some sat navs that show the permante speed cams…
there is a point beyond the location your trying to warn drivers about by flashing etc. after a mile or so I`ve passed the hazzard, I stop doing it as it only confuses drivers, hopefully theres someone behind me who is closer and will warn em
Driveroneuk:
well quite obviously it means “slow down” as there is some kind of problem ahead be it police, stationary traffic, accident, whatever. Back off!I used to flash trucks on the m/way that were approaching stationary traffic, but with todays powerful brakes, use of hazard warning lights, etc. etc. I don’t bother anymore. (+ because some used to just flash & wave back
I flash and wave back as thanks for their help and to confirm I have noticed their signal. But as we all know flashing lights and other non-official signals are open to misinterpretation. However, if there is staionary traffic or another hidden hazard I usually give fellow truckers 3 longish flashes. As for the (becoming more frequent) muppetts on the wrong side of a dual carriagway I lose count of how many flashes they get 
Even had a Business Post rigid do it on Tyburn Road in Birmingham.
give a repeated headlight flash and a “thumbs down” for a speed trap (Or at least, I would do if it wasn’t illegal
can’t get my head around why this should be illegal.
Speed cameras( mobile or fixed) were originally installed not to catch speeders but to deter them from speeding.
All the publicity from safety campaigners stress that the idea is to stop drivers from speeding.
Surely warning other drivers of them is fullfilling the same purpose. 
Perhaps the cynics amongst us would say that the fine has something to do with it
I still do it even though I just drive my little white Sprinter so for any that see me, please take note, I AM warning you about an upcoming problem
ps still got my CB fitted as well so will be shouting on '19 to
thumb down . it either means , speed trap ahead or some other hazard OR IVE JUST ■■■■■■ and may have followed through.
Had it today infact on the A66 Scotch Corner - Penrith. Well, not exactly thumbs down, but flashing and waving palm down.
Turns out there was a truck stopped just ahead where the road is not dual carriagway, with a puncture on his trailer. Tyre man was there with his van sorting it.
Truck driver had used sense and stopped where the road was wider as there was a right turning lane for a side road.
Incidentally, for anybody who uses this route, the Temple Sowerby by-pass is now open & its grand 