The driver of a motor vehicle shall make such signals and on such occasions as may be prescribed by the Central Government:
Provided that the signal of an intention to turn to the right or left or to stop
(a) in the case of a motor vehicle with a right-hand steering control, may be given by a mechanical or electrical device of a prescribed nature affixed to the vehicle; and
(b) in the case of a motor vehicle with a left-hand steering control, shall be given by a mechanical or electrical device of a prescribed nature affixed to the vehicle
Provided further that the State Government may, having regard to the width and condition of the roads in any area or route, by notification in the Official Gazette, exempt subject to such conditions as may be specified therein any motor vehicle or class or description of motor vehicles from the operation of this section for the purpose of plying in that area or route.
Legal Commentary & Landmark Judgments: Section 121
Section 121 of the Motor Vehicles Act, 1988 mandates that drivers give prescribed manual or mechanical/electrical signals prior to turning or stopping, establishes differentiated device standards for right-hand and left-hand drive vehicles, and empowers State Governments to grant localized exemptions.
In rear-end and side-collision cases, examine eyewitnesses and mechanical inspection reports specifically regarding brake-light activation and turn-indicator function. If the defendant vehicle executed a sudden U-turn or right turn across oncoming traffic without activating mechanical turn indicators under Section 121, plead statutory negligence per se to defeat claims of contributory negligence against the following vehicle.