A dual mode mobile terminal (30) is capable of communicating (e.g., with a core network) either via a first radio access network (12) having a first type radio access technology (GSM) or a second radio access network (14) having a second type radio access technology (UTRAN). When conditions warrant, a network node prepares a radio access technology (RAT) handover message for transmission to the equipment unit (UE) in conjunction with handover of the mobile terminal (MT) from the first radio access network to the second radio access network, and an associated change of operation mode of the mobile terminal (MT) from the first mode to the second mode. In accordance with the present invention, a radio access technology handover message includes a first information element representative of a first parameter from which a value of a second parameter can be derived so that the second parameter need not be included as a separate information element in the radio access technology handover message. Not including the second parameter as a separate element in the radio access technology handover message facilitates non-segmentation of the radio access technology handover message. In one aspect of the invention, the radio access technology handover message is a RRC Handover to UTRAN message; the first parameter is a Serving-Radio Network Temporary Identifier (S-RNTI 2); and, the second parameter is an information element which facilitates distribution of load and transmission of traffic in the radio access network (e.g., a Default DPCH Offset Value).