A sudden traffic surge immediately after special events (e.g., conventions, concerts) can create substantial traffic congestion in the area where the events are held. It is desired that the special events related traffic performance can be measured so that the traffic flow can be improved via some existing methods such as a temporary traffic signal timing adjustment. This paper focuses on the study of the arterial travel time prediction using the Kalman filtering and estimation technique, and a graduation ceremony is chosen as our case study. The Global Positioning System (GPS) test vehicle technique is used to collect after events travel time data. Based on the real-time data collected, a discrete-time Kalman filter is then applied to predict travel time exiting the area under study. An assessment of the performance and its effectiveness at the test site are investigated. The approaches to further improve the accuracy of the prediction error are also discussed.