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The paper presents a real decision problem regarding the issue of planning the supply of LPG (a popular fuel in Poland) to petrol stations. A description of the elements of the decision problem is presented: inventory in station readings and forecasts, petrol station categorization, and planning and scheduling of tank truck delivery journeys. A linear programming model for Vehicle Routing Problem with Time Windows (VRPTW) was used to optimize routes. Planning and scheduling are developed for a three-day time horizon. The presentation contains a detailed description of the specifics of fuel supplies in the Polish market. Thus, the necessary modifications of the original VRPTW model are developed. The key change implemented by the research team was to make service station selection more flexible with the stock levels planned to be replenished on a specific date. Thanks to these adjustments, the modified VRPTW model better assigns fuel stations to the generated routes, which translates into more favorable values of the selected goal function (we anticipate the possibility of optimizing both route lengths, CO2 emissions, as well as the use of a metacriterion that considers both goal functions). However, it should be noted that the degree of improvement of the solutions depends on the specificity of the geographical region for which the calculations were performed. The paper also presents problems with the practical implementation of the proposed changes in the VRPTW model.
Keywords: VRPTW, delivery planning, optimization, VMI concept© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.