The themes of this monograph include modern engineering problems of marine traffic engineering, focusing on what this discipline deals with: navigational safety assessment methods. These include: • criteria of assessing navigational safety in restricted areas, • navigation risk, as a complex criterion of navigational safety assessment in waterway systems, • models of navigation risk determination used worldwide, • conditions of safe operation of ships on waterways determined by using navigation risk, • minimum safe tug assistance on port waterways, • navigation risk management in waterway systems with a description of a computer program for model-based tests of navigational safety on Southern Baltic waterways.