Efficiency and safety in cold warehouses: a combined approach for storage and routing optimisation

This paper proposes an analytic optimisation model that combines storage assignment and routing strategies for minimising the picking time in a single-block warehouse of frozen food products. In cold storage, not only the quality of the products must be preserved, but also the health of the workers, by limiting their exposure to low temperatures. The model first examines the risk of item damage during the picking process and proposes a systematic reallocation of products based on two weight classes, ensuring that heavier items are retrieved first while lighter ones are handled at the end of the picking tour. Then, two hybrid routing heuristics (‘S-shape with return’ and ‘adapted midpoint’) are incorporated into the allocation strategy, generating optimised picking sequences that adhere to precedence constraints. The proposed framework achieves a significant reduction in picking time, which turns out to be approximately 40% lower than the baseline scenario under optimal conditions, thereby minimising workers’ exposure to unsuitable temperatures while preserving product integrity. Furthermore, reducing order processing times enhances fulfilment efficiency and reduces operational costs, contributing to a more sustainable and competitive cold chain logistics system.