A car's turn signals, brake lights and horns are essential signals marking the vehicle's direction and intentions, but a bicycle has none of these important safety features. Instead, cyclists use a coordinated set of hand signals to announce their intentions to both cars and other cyclists.
Announce a turn by pointing in the direction you wish to go with your arm held straight out from your shoulder. Use your right arm to point right and left arm to point left. Another method to signal a right turn is the same as the manual signal from a car driver: Hold your left arm out from your body with your hand raised above your shoulder (at a 90-degree angle).
Slowing and Stopping
Signal a stop or braking with your left or right arm held out from your body with your elbow angled so that your hand hangs straight down (at a 90-degree angle). It is also acceptable to hold your arm straight downward with your hand below your waist.
To merge into another lane or a gap in a paceline, simply point to the spot in the road where you'd like to merge.
Point out road hazards such as gravel and potholes by pointing straight at the hazard as you pass it. If possible, anticipate hazards and signal early, or mimic the signals of leaders in a paceline to give riders behind you plenty of warning.
Blocked Lanes and Passing
A rider in a paceline should signal passing by sweeping the right arm (if passing to the left) straight back in a swimming motion to show that those behind should be prepared to move over. If passing to the right, use the left arm to signal.