(A)   No person shall turn a vehicle at an intersection unless the vehicle is in proper position upon the roadway as required by ordinance, or turn a vehicle to enter a private road or driveway or otherwise turn a vehicle frost a direct course or move right or left upon a roadway unless and until the movement can be made with reasonable safety.  No person shall so turn any vehicle without giving an appropriate signal in the manner hereinafter provided in the event any other traffic may be affected by the movement.
   (B)   A signal of intention to turn right or left when required shall be given continuously during not less than the last 100 feet traveled by the vehicle before turning.
   (C)   No person shall stop or suddenly decrease the speed of a vehicle without first giving an appropriate signal in the manner provided herein to the driver of any vehicle immediately to the rear when there is opportunity to give the signal.
   (D)   When any person is properly preparing for, attempting or executing a left turn, as described in division (A) of this section, no other person operating another vehicle immediately following the turning vehicle shall pass or attempt to pass the turning vehicle to the left. Such other person shall come to a complete stop if necessary at a safe distance behind the person preparing for, attempting or executing the turn or may proceed to the right of the turning vehicle as provided by 47 O.S. § 11-304 and § 20-88 of this code of ordinances.
(47 O.S. § 11-604)  (`90 Code, § 20-55)