law: The Motor Vehicles Act, 1988
  121. 
  
  Signals  and signalling  devices.
  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-
  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.