Reliable and secure communications are essential during the transport of Category I nuclear material. Communications by two-way radio concerning the transport of such nuclear material should consist of encrypted messages only. During the transport, the escort should remain in frequent contact with the shipper, the receiver, the local authorities and the response forces along the transport route. When planning for the shipment, the shipper should establish a plan of action in the event that communications are lost during shipment. The establishment of a transport security control centre should be considered.