Section 79(3)(a) in The Bihar Motor Vehicles Rules, 1992
(a)that the vehicle shall not be driven in a public place except by the permit holder or a driver authorised by him in writing and approved by the Regional Transport Officer or Asstt. R. T. O., as the case may be which writing an approval shall be carried by such driver when driving and shall, on demand by any police officer or officer of the Motor Vehicle Department of and above the rank of an Asstt. Motor Vehicle Inspector, in uniform, produce such authorisation for examination;