For different reasons, models sometimes get blocked and a single time step can take a very long time to complete. When this happens, the software can appear to freeze and attempts to pause or stop playback may not be recognised. In this state there is no graceful way to proceed and you may be tempted to force the software to close down. To get around this, there is a feature called Automated Blockage Detection (ABD) in LEGION Simulator. For more information, see Detecting blockages automatically .