When we arrived in the states my DH had to get a California license and they did expect him to know hand signals. So from this info I knew how I was suppose to signal on my bike but I agree with the girls most drivers dont seem to get the bent left arm thing. I just stick out a straight right or left to signal which direction I will be going it saves confusion and that has to be a good thing.
The most effective way to do it, is to do it.
Amelia Earhart
2005 Trek 5000 road/Avocet 02 40W
2006 Colnago C50 road/SSM Atola
2005 SC Juliana SL mtb/WTB Laser V