Due to the strong interrelations between traffic situations at different locations of a road network the traffic control actions applied for solving a local traffic problem can create another traffic congestion at a different location in the network. This can result the average travel time on the network level, even after the application of the control actions, to be the same or worse. Therefore, coordinative control strategies are required to make sure that all available control actions serve the same objective. In this paper, an intelligent decision support system based on multi-agent approach is proposed to assist the human operator of the road traffic control centre to manage the current traffic state. In the proposed system, the total network is divided in sub-networks, each of which has its own evaluation agent. In the proposed system the agent will be able to react with other (affected) agents through a high level agent called coordinator to find the optimal global traffic control action using an intelligent traffic control. The capability of the proposed multi-agent-based decision support system was tested for a case study of a part of the traffic network in the Riyadh city of Saudi Arabia. The obtained results show the ability of the proposed multi-agent-based system to identify the optimal global control action.