51. The holder of a chartered transport permit is authorized, at the request of another holder, to resume a trip begun by the latter if his bus becomes inoperational during the trip.
If the bus used as a replacement is in a higher category, the holder is not entitled to increase the price of the trip.
If it is in a lower category, the holder is entitled to reduce the price of the trip in relation to the remaining distance to be covered or to the time required to cover that distance, as the case may be.
If the price is calculated at an hourly rate, the holder shall in no case take into account any waiting time owing to the breakdown of the bus.