VEHICLE CODE § 22107
No person shall turn a vehicle from a direct course or move right or left upon a roadway until such movement can be made with reasonable safety and then only after the giving of an appropriate signal in the manner provided in this chapter in the event any other vehicle may be affected by the movement.
Washam v. Peerless Automatic Staple Mach. Co. (1941) 45 Cal.App.2d 174 provides great guidance in understanding CVC § 22107. In that case, the Court held that a motorist about to turn left is not required to leave his automobile and scan the horizon or by trigonometrical computations calculate the yards distant of the approaching automobile to insure his own safety against a collision with one who ignores the law and the rights of others lawfully within an intersection. In short, a left turn should be made only when it can be done with reasonable safety.
In People v. Carmona (2011) 195 Cal.App.4th 1385 the Court held that there was no reasonable possibility that motorist violated the statute requiring a turn signal “in the event any other vehicle may be affected by the movement,” in turning right without signaling when a police car was 55 feet away from motorist and approaching in the oncoming lane, and thus there was no reasonable suspicion supporting a traffic stop, where there was no potential for the turn to affect the police car, and there were no other vehicles in the vicinity.
