Guys you will have to excuse my ignorance but I need some info, I have been driving since 1978 and I am still learning, now we all use our lights and indicators to signal one anothr on the road and the majority of drivers understand the sequence, but HOW do you signal oncomming traffic on the motorway that there is an accident or the motorway ahead is blocked get off at the next slip etc ?
I was comming from Newbury today towards London (between j12 and j13) an artic had gone through the side barrier into a slight ditch west bound but the traffic was some where in the region of five miles pluss at a complete standstill, there were lots of trucks heading west and could of avoided the situation if they had got off at j12, but I was not sure how to tell them, I dont have a breaker breaker 10.4 and dont have a big enough mouth to shout, I DID however flash my lights repeatedly at some of the company trucks I know but after getting funny looks I stopped, so what is the answer, does any one have a clue,
Unless you’ve got both got CBs or know each others phone numbers, you can’t do [zb]. Thumbs down signal can give a general idea of trouble ahead, but it usual signals for plod or vosa, not a closure. Certainly no trucker would turn off at the next slip because you’ve given a thumbs down signal anyway. Just get on with your job and let them sort themselves out.
Rob K:
Unless you’ve got both got CBs or know each others phone numbers, you can’t do [zb]. Thumbs down signal can give a general idea of trouble ahead, but it usual signals for plod or vosa, not a closure. Certainly no trucker would turn off at the next slip because you’ve given a thumbs down signal anyway. Just get on with your job and let them sort themselves out.
DIY
Don’t involve yourself 
The highways agency have spent hundreds of thousands by putting up gantry signs, cameras, using 4x4 patrols and have a 24 hour link to the national media. They still don’t warn you until it is too late, so what chance has one man with a thumb and an overactive flasher stalk got?
Wheel Nut:
Rob K:
Unless you’ve got both got CBs or know each others phone numbers, you can’t do [zb]. Thumbs down signal can give a general idea of trouble ahead, but it usual signals for plod or vosa, not a closure. Certainly no trucker would turn off at the next slip because you’ve given a thumbs down signal anyway. Just get on with your job and let them sort themselves out.
DIY
Don’t involve yourself
The highways agency have spent hundreds of thousands by putting up gantry signs, cameras, using 4x4 patrols and have a 24 hour link to the national media. They still don’t warn you until it is too late, so what chance has one man with a thumb and an overactive flasher stalk got?
Be fair sometimes they’re so considerate and enthusiastic they even warn you about a problem that was cleared hours ago. 
And for the OP’s benefit it’s breaker 19 if you want to use a CB to say something and 10/4 if you’ve received it.
Won’t work on a motorway but a way to let oncoming traffic know they’re approaching an accident is to flash them a couple of times then punch your fist into the palm of the other hand.
However there are a couple of small problems with this signal 
- it means driving without any hands on the steering wheel
and
- if anyone misunderstands the signal they’re likely to come after you and give you a smack in the mouth
I tried this last week and the people I signalled looked shocked angry and confused when they saw me do it 
Mind you we were standing at opposite ends of a bar at the time so … 