  High-tech giants and start-ups are investing in drone technologies to provide
urban air delivery service, which is expected to solve the last-mile problem
and mitigate road traffic congestion. However, air delivery service will not
scale up without proper traffic management for drones in dense urban
environment. Currently, a range of Concepts of Operations (ConOps) for unmanned
aircraft system traffic management (UTM) are being proposed and evaluated by
researchers, operators, and regulators. Among these, the tube-based (or
corridor-based) ConOps has emerged in operations in some regions of the world
for drone deliveries and is expected to continue serving certain scenarios that
with dense and complex airspace and requires centralized control in the future.
Towards the tube-based ConOps, we develop a route network planning method to
design routes (tubes) in a complex urban environment in this paper. In this
method, we propose a priority structure to decouple the network planning
problem, which is NP-hard, into single-path planning problems. We also
introduce a novel space cost function to enable the design of dense and aligned
routes in a network. The proposed method is tested on various scenarios and
compared with other state-of-the-art methods. Results show that our method can
generate near-optimal route networks with significant computational
time-savings.
