Performance evaluation of compact automated parking systems with mobile application and customer service priority

We study a recently introduced smart compact automated parking system (CAPS), deploying straddle carriers, which require little footprint area. The straddle carriers can elevate and move a car over other cars in the horizontal direction in deep storage lanes, thereby considerably increasing the car storage capacity. Customers can reserve a parking space with a mobile application, or just drive in. Customers with booking by mobile application receive priority over the drive-in customers. We build priority queueing network models to evaluate the performance of a CAPS with priority booking under two storage policies. We then develop approximation methods to solve the analytical models and validate them through simulation. Numerical experiments show that the waiting time of a customer with booking can be reduced by 9.2% and 3.4%, respectively, for the dedicated and shared storage policies, compared with systems without priority booking. Then we compare the dedicated and shared storage policies and conduct a sensitivity analysis on the arrival rates of two types of cars. To minimise the expected retrieval time, the optimal ratio of width to height should be around 1.3. Finally, we calculate the investment cost of a CAPS and compare it with a competitive cylindrical automated parking tower.