In the daily activity of regional railway traffic, when the circulation frequencies are high, any anomaly that alters the scheduled circulation of trains may distort any of all of the established timetables and involve re,scheduling many of services, due to the numerous possible alternatives for resolving the situation. An on-line model is presented in this article which helps in choosing the most appropriate solution based on an intelligent exploration of the solutions space. The tool has been implemented in the Spanish national railways company. (C) 1999 Elsevier Science Ltd. All rights reserved.