VELOS is a Virtual Reality (VR) system that aims to enable researchers in Naval Architecture and Marine Engineering as well as designers, operators and inspectors to assess, early in the design process, passenger and crew activities on ships during normal (comfortability, ergonomy) to hectic (evacuation) conditions of operation and improve ship design accordingly. VELOS constitutes an extension of VRsystem, a generic multi-user VR system, that provides broad range functionality that includes geometric- and VR-modeling, crowd microscopic modeling, through a library of nearly 20 steering behaviors, as well as communication with seakeeping software modules for improving environments realism and accounting of ship-motion effect on passengers movement. After discussing the structure of VRsystem, the present paper focuses on presenting and illustrating for the stern vertical zone of a ro-ro passenger ship the evacuation-specific functionality, that VELOS is currently being endowed with. This functionality enables VELOS user to:  interactively build a topological model of the zone, where evacuation scenario is to be materialized, in order to improve the efficiency of path planning processes that are executed during the evacuation scenario.  efficiently prepare the required input (e.g., passenger demographics, maximum walking speed allocation, passenger/crew initial spatial distribution) for executing evacuation scenarios.  possess all output information (e.g., agent-location time histories, crowd densities in user-specified sites), that is required for monitoring the materialization of evacuation scenarios as well as performing statistical analysis of the output data collected at the end of a simulation session.