Section 219(1)(a) in The Bihar Motor Vehicles Rules, 1992
(a)if the brakes of the trailer or trailers cannot by the driver of the drawing motor vehicle or by some other persons carried on that vehicle:-(i)one person on every trailer competent to apply the brakes, and(ii)one person placed at or near the rear of the last trailer in train in such a position as to be able to have a clear view of the road in rear of the trailer, to signal to the drivers of overtaking vehicles and to communicate with the driver of the drawing motor vehicle,