Abstract: A turn indicator system determines when a moving vehicle has completed a turn and automatically turns off a turn indicator light. The system includes turn indicator lights, an accelerometer, and a processor. The accelerometer can sense acceleration in two-axis or three-axis. The processor is configured to receive the sensed accelerometer data and to determine when a vehicle has completed a turn based on the received accelerometer data. In response to determining that a turn is completed, the processor signals the appropriate turn indicator light to turn off. The turn indicator system can be implemented in a single-track vehicle, such as a bicycle or a motorcycle, or in a multi-track vehicle, such as an automobile.