The mobile network operators (MNOs) have considered the provision of simultaneous multiple access in heterogeneous networks. Access network discovery and selection function (ANDSF) is introduced to provide simultaneous multiple access in heterogeneous networks to users. Since a ANDSF manages the inter-system mobility and routing policy, it can mitigate congestion of a certain access networks by restricting access or IP traffic flows toward the crowded access network. However, for congestion control by ANDSF, ANDSF should enable to manage the congestion condition among heterogeneous networks. Thus, this paper proposes messages and procedures for ANDSF to collect the congestion condition among heterogeneous networks and to decide inter-system mobility and routing policy. The proposed messages and procedures can be easily implemented by extending the messages and procedures defined in the 3GPP standards.