Shuttle-based operating policies for multiple-lift compact automated parking systems based on queuing networks

We study a new multiple-lift compact automated parking system, which is a new technology with a circular structure using carousel equipped with the shuttles for the horizontal movement and multiple lifts equipped with the platforms for the vertical movement. This paper investigates dedicated and random shuttles operating policies. We divided the carousel into areas based on the number of lifts. We propose a dedicated shuttle operating policy under which each area shuttles can only serve one dedicated lift. A random shuttle operating policy under which shuttles can serve any lift. We get expected throughput time models for the two shuttle operating policies under the same system physical configurations based on queuing network models. We compare the analytical models with simulation models, and the results show that the proposed models provide accurate estimates. A numerical experiment is conducted to illustrate the trade-offs between dedicated shuttle and random shuttle operating policies. The results show that the retrieval time in random shuttle operating policy is larger than the retrieval time in dedicated shuttle operating policy. We also get the optimal system structure, including the number of the lifts.