An adaptive signal control system with an online signal performance measure is introduced. Unlike conventional signal control systems, the proposed method uses real-time delay estimation and an online signal timing update algorithm. As a signal performance measure, intersection delay for each phase is measured in real-time via an advanced surveillance system that reidentifies individual vehicles at upstream and downstream stations by using vehicle waveforms obtained from advanced inductive loop detectors. In each cycle, the signal timing plan is optimized based on the delay estimated from the vehicle reidentification technology. The main thrust of the algorithm is the online control capability utilizing direct intersection delay measures. A description of the overall control system architecture and the optimization algorithm is addressed. Performance of the proposed system is evaluated with a high-performance microscopic traffic simulation program, Paramics, and the preliminary results prove the promising properties of the proposed system.