The use of Lagrangian trajectories for the identification of the environmentally safe fairways

► Offshore areas are quantified in terms of the probability of transport of pollution to vulnerable regions. ► A method for the identification of the optimum fairway minimising environmental risks is developed. ► Measures of gain from the use of an optimum fairway are introduced. ► The gain from the use of the optimum fairway is 40% in terms of the probability of coastal pollution. ► The use of the optimum fairways almost doubles the typical time during which the released pollution reaches the coast.