Using hand signals while on a bike is just as important as a driver using turn signals on the road. Bikes are supposed to abide by the same rules as drivers, so it's very important for them to communicate with those around there. 

As a biker, one might already know the hand signals. However, others around you (like drivers) might not know what you're doing. Evanston's Transportation and Parking Committee near the Chicago, Illinois area proposed a new program that would implement signs along the road that allows bikers, drivers, and motorists the signals for more effective communication on the road. 

An easy solution to this issue would be to put turn signals on bikes. Though that probably won't happen anytime soon, there was a new idea introduced by a startup at the University of Illinois that will allow you to wear turn signals. The product is still under development, but it could be the future of bike safety. Check out how it works here. 

For those that don't know the hand signals, check out this step-by-step video within Illini Live's segment on All Things Bikes on how to use each hand signal while on the bike. Also check out the video if you're a driver so you know what the biker in front of you is trying to tell you.