Collision avoidance is a priority task for ensuring the safety of a maritime transportation system. However, for a ship towing system, which is characterized by multiple vessels and physical connections, the research works about collision avoidance is limited. Thus, this paper proposes a speed and heading control-based conflict resolution of a ship towing system for collision avoidance. Two systems compose the core of the proposed conflict resolution: the risk assessment system and the coordination control system. The risk assessment is to identify the conflict and determine the time of avoiding action by calculating the index of conflict and the available maneuvering margin. The coordination control is based on the model predictive control (MPC) strategy to cooperatively control two tugboats for regulating the position, heading, and speed of the manipulated ship. Simulation experiments show that according to the index of conflict, the time cost, and the fuel consumption, a selected operation of combined heading and speed can be recommended for a ship towing system to provide a safer and more efficient towage manipulation.

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The functional efficiency of the pervious pavement is evaluated in terms of skid resistance and tire/road noise, which determines the highway safety and comfort benefits to the travellers. The primary objective of this paper is to incorporate the functional performances such as frictional and acoustic characteristics into the pervious pavement design procedures. The existing pervious pavement design procedures assume that the functional requirement is satisfied arbitrarily with the volumetric and composition requirement. This paper formulates the functional design of porous mixture as the bi-objective optimization model, which maximizes the skid number and minimizes the tire/road noise level, both were obtained from the numerical simulation models. A fast nondominated sorting genetic algorithm (NSGA II) was adopted as the solution algorithm to solve the optimization model. Pareto solutions from this model indicate that the performance of skid resistance could not be improved without increasing the tire/road noise. The optimum solutions for this model were selected as the appropriate trade-off between both the parameters. This model allows a highway agency for the incorporation of frictional and acoustic parameters into the existing pervious pavement mixture and thickness design procedures.@en