I think that riding through many new towns and cities a cyclist is bound to not have a good understanding of drivers attitudes. Signaling helps. The reason I’m thinking of this subject is because I was riding in Brooklyn and some guy rode by me and did what’s in this image showing “right turn”. My thought was – no driver is going to understand what that means. These signals were made for drivers way back before cars had turn signals. And all these signals use the left arm because a driver could not safely stick their right arm out the window. To use this Right Turn signal while riding a bicycle is silly.

As a bike rider we can use either arm to make a turn signal.

Left turn = left arm extended
Right turn = right arm extended

Keep it simple.