I was driving down the street the other day and came up to a cement mixer at a stop light. When the light turned green about 30 gallons of reddish cement-water and small rocks sluced out the back as the cement mixed sped up. Luckily no one was behind it when it happened. I started honking and waving my hands to try and let the driver know what was going on, but because the cement truck was higher than my car I couldn't really tell him anything, and he couldn't see my lame hand signals for "crap is shooting out the back of your truck". All that happened was he looked at me like I was crazy as he drove off.
So, my question is: is there some sort of international trucker signal for "you have a dangerous condition and your load could very well kill somone"? Is there something better to do than waving your arms and honking?