A Vertiport Location Method for Urban Low-Altitude Air-Ground Coordinated Transportation

Against the backdrop of the rapid development of the low-altitude economy, urban air mobility (UAM), which employs electric vertical take-off and landing (eVTOL) aircraft as the carrier, has emerged as a new pathway to breaking through urban traffic bottlenecks. Vertiport siting is the key to achieving efficient air-ground coordination between low-altitude and ground transportation. Existing studies neglect the probability distribution of users'travel willingness and fail to quantify the impact of air traffic on ground road network flow allocation during the dynamic air-ground interaction. To address this gap, an air-ground parallel operation mode of “non-motorized access-egress + eVTOL” is proposed, and a travel willingness probability model for the urban air-ground coordinated transportation network is developed, based on the multinomial logit (MNL) model, to characterize users' choice behavior between pure ground travel and low-altitude travel. A bilevel programming model for vertiport siting is then established, with the upper layer devoted to location decision-making and the lower layer to user equilibrium assignment; the ground impedance is calculated by the Bureau of Public Roads (BPR) function, and the interaction mechanism between air and ground traffic is quantified through an iterative coupled solution of“ground impedance-mode choice probability-demand reallocation.”Numerical results show that an optimal number of vertiports exists in the air-ground coordinated network: in the case study, the operating benefit reaches its peak of 87 200.74 yuan when the number of vertiports B is 6, and the network traffic impedance is improved by nearly 14% relative to the pure ground network. The resulting low-altitude network reshapes users' travel mode choices and origin-destination (OD) demand allocation by diverting flow from critical links, thereby forming an air-ground coupling mechanism of “demand shift-flow optimization-efficiency improvement.”It is further found that once the unit eVTOL fare exceeds 7 yuan, both users' low-altitude travel willingness and the mitigating effect of air traffic on ground impedance decline significantly.