A Geometric Analysis-Based Safety Assessment Framework for MASS Route Decision-Making in Restricted Waters

TL;DR

This paper tackles safe MASS routing in irregular restricted waters by introducing GARSA, a geometric analysis-based framework that leverages a dynamic width characterization function (ω_dwc) derived from boundary elements to quantify navigable space along routes. It constructs a Safety Performance Index (κ_sp) that balances global route width with local narrow sections, enabling objective comparison of candidate paths, and uses a Dynamic Window Approach (DWA) to modify routes while respecting ship kinematics. The approach is validated in a Port of Hamburg simulation, where GARSA identifies safer routes, visualizes width variations with heatmaps, and demonstrates the advantage of safety-driven routing over purely distance-based planning through comparisons with A*. The findings suggest that geometry-informed safety assessment and DWA-based refinement can significantly reduce collision risk in complex constrained waterways and provide practical decision-support for MASS deployment, with potential for real-world adaptation across varied ports and vessel types.

Abstract

To enhance the safety of Maritime Autonomous Surface Ships (MASS) navigating in restricted waters, this paper aims to develop a geometric analysis-based route safety assessment (GARSA) framework, specifically designed for their route decision-making in irregularly shaped waterways. Utilizing line and point geometric elements to define waterway boundaries, the framework enables to construct a dynamic width characterization function to quantify spatial safety along intricate waterways. An iterative method is developed to calculate this function, enabling an abstracted spatial property representation of the waterways. Based on this, we introduce a navigational safety index that balances global navigational safety and local risk to determine the safest route. To accommodate ship kinematic constraints, path modifications are applied using a dynamic window approach. A case study in a simulated Port of Hamburg environment shows that GARSA effectively identifies safe routes and avoids the risk of entering narrow waterways in an autonomous manner, thereby prioritizing safety in route decision-making for MASS in confined waters.

Figures (10)

• Figure 1: Decomposition of the Waterway
• Figure 2: Illustrative Example of Dynamic Width Characteristic
• Figure 3: Illustration of the Relationship between an MASS Movement and Geometric Elements. (a) Line feature. (b) Point feature.
• Figure 4: Sketch of the Waterway Intersection Condition
• Figure 5: Diagram of the Safety Route Decision Support Process