Package delivery via autonomous drones is often presumed to hold commercial and societal value when applied to urban environments. However, to realise the benefits, the challenge of safely managing high traffic densities of drones in heavily constrained urban spaces needs to be addressed. This paper applies the principles of traffic segmentation and alignment to a constrained airspace in efforts to mitigate the probability of conflict. The study proposes an en-route airspace concept in which drone flights are directly guided along a one-way street network. This one-way airspace concept uses heading-altitude rules to vertically segment cruising traffic as well as transitioning flights with respect to their travel direction. However, transition flights trigger a substantial number of merging conflicts, thus negating a large part of the benefits gained from airspace structuring. In this paper, we aim to reduce the occurrence of merging conflicts and intrusions by using a delay-based and speed-based merge-assist strategy, both well-established methods from road traffic research. We apply these merge assistance strategies to the one-way airspace design and perform simulations for three traffic densities for the experiment area of Manhattan, New York. The results indicate, at most, a 9–16% decrease in total number of intrusions with the use of merge assistance. By investigating mesoscopic features of the urban street network, the data suggest that the relatively low efficacy of the merge strategies is mainly caused by insufficient space for safe manoeuvrability and the inability for the strategies to fully respond and thus resolve conflicts on short-distance streets. ... Read more

The paradigm of large-scale adoption of autonomous drone delivery promises to provide commercial and societal benefits. Over the past years, several companies have investigated the use-case of drones to transport small express packages of fast-food meals and time-sensitive medical supplies. The latter has shown to be highly beneficial in many parts of the worldwhere traditional transport infrastructure remains largely non-existent. However, it is assumed that the true value of autonomous delivery drones can only be demonstrated when it is applied to urban environments. For example, the use of a large-scale fleet of autonomous drones to transport packages within the last-mile segment could potentially improve the economics of package delivery, reduce traffic congestion and help decrease the total anthropogenic carbon dioxide emissions in cities. In addition, supplementing the existing last-mile delivery system with this new technology could also help accelerate the European Union’s 2050 vision of de-carbonising the transport sector. Autonomous drone delivery is obviously not a panacea to the above problems. It could, however, offer a path to mitigate such societal problems. Yet, even though there is a compelling case for autonomous drone delivery, it still remains to be deployed in cities. The reasons for this slow adoption include a large number of complex regulatory hurdles that vary between countries and cities. However, the biggest challenge is how to safely harbour large traffic volumes of drones in a constrained urban environment. This thesis frames the scientific problem and outlines twomain past research areas: unconstrained airspace design and road-based design, which served as a rich source of inspiration for this research. In a past study, known as theMetropolis project, it was demonstrated that layering the airspace and allocating flights to different altitude layers with respect to travel directions helped to mitigate the conflict probability in an unconstrained airspace setting. The study revealed two factors that were largely responsible for increasing the level of airspace safety, namely, segmentation of traffic and reduction of the relative speed, by traffic alignment, between cruising traffic at the same altitude. Furthermore, existing road vehicles, especially automated cars, provide an informative comparison with autonomous drones. Both emerging transportation modes are expected to navigate in constrained urban settings and operate in high traffic density scenarios. Of course, there are notable differences, for example, drones will operate in a three-dimensional space and the current performance limits of drones imply that it would not be optimal for drones to come to a sudden halt at intersections unlike cars and thus separating opposing traffic flows at intersections will be a difficult task. Yet, road design and research has evolved alongside road vehicles to include a host of safety measures in effort to make roads and streets safer for all its users. They make use of various conflict prevention measures to structure and organise traffic flows. Current roads and streets have channelisation planes, which help separate opposite flows of traffic using road markings, islands and raised medians to distinguish and support one-way and two-way streets. These forms of structuring have shown to reduce of the risks of conflicts and, to an extent, are able to safely harbour high traffic densities in highly constrained urban environments. The work in this thesis therefore aimed to investigate what design paradigms and methodologies from unconstrained airspace research and road infrastructure design can be translated to a constrained urban airspace for high-density drone traffic operations... ... Read more

Drone-based delivery is likely to reduce energy and greenhouse gas emissions associated with the transport of small express packages, fast-food meals and medicines, especially when deployed in large-scale in urban areas. However, it is an enormous challenge to facilitate such high traffic densities in constrained urban environments. A recent study applied the principles of traffic alignment and segmentation to the constrained urban airspace of Manhattan, New York, in an effort to mitigate conflict probability. In that study, two novel airspace concepts were proposed, namely, the two-way and one-way concept. Both concepts employed a heading-altitude rule to vertically segmented traffic with respect to their travel directions. In addition, the one-way concept also featured horizontal constraints to promote unidirectional traffic flow. These concepts bear resemblance to that of road-based traffic. Further, both concepts featured transition altitudes to accommodate turning flights that need to decelerate to safely perform turns at intersections. The comparative study showed the one-way airspace configuration to be more effective than the two-way concept in terms of safety. In the pursuit of demonstrating our understanding of the intricate differences between the two-way and one-way airspace configurations, this paper aims to explore and analyse salient conflict properties. By using fast-time simulation experiments, the different types of conflicts are captured and analysed for multiple traffic demand levels. Our results suggest that conflicts are largely caused by flights climbing or descending to their respective altitude layers. For both concepts, the merging conflicts consisted of in-trail and crossing conflicts, while the two-way also contained a high proportion of head-on conflicts. Our study therefore sheds light on the different categories of conflicts that could help guide future research in airspace design in constrained urban areas. ... Read more

Large-scale adoption of drone-based delivery in urban areas promise societal benefits with respect to emissions and on-ground traffic congestion, as well as potential cost savings for drone-based logistic companies. However, for this to materialise, the ability of accommodating high volumes of drone traffic in an urban airspace is one of the biggest challenges. For unconstrained airspace, it has been shown that traffic alignment and segmentation can be used to mitigate conflict probability. The current study investigates the application of these principles to a highly constrained airspace. We propose two urban airspace concepts, applying road-based analogies of two-way and one-way streets by imposing horizontal structure. Both of the airspace concepts employ heading-altitude rules to vertically segment cruising traffic according to their travel direction. These airspace configurations also feature transition altitudes to accommodate turning flights that need to decrease the flight speed in order to make safe turns at intersections. While using fast-time simulation experiments, the performance of these airspace concepts is compared and evaluated for multiple traffic demand densities in terms of safety, stability, and efficiency. The results reveal that an effective way to structure drone traffic in a constrained urban area is to have vertically segmented altitude layers with respect to travel direction as well as horizontal constraints imposed to the flow of traffic. The study also makes recommendations for areas of future research, which are aimed at supporting dynamic traffic demand patterns. ... Read more

Road traffic delay and urban overcrowding are increasing rapidly all over the world. As a result, several companies have proposed the use of small unmanned aerial vehicles (sUAVs) as an alternative to road-based transportation. These small autonomous drones are expected to operate within a thin airspace band (Very Low Level) in high traffic densities in constrained urban environments. This presents a challenge for ensuring the safe separation and efficient routing of drone flights. Current research has made modest progress towards finding solutions for conflict detection and prevention in highly dense and constrained environments (e.g., in-between buildings). In this paper, the state of the art of urban airspace design and conflict prevention and resolution research are discussed, and their applications to constrained environments. Additionally, fasttime high-fidelity simulations of high-density traffic scenarios are used along a non-orthogonal city layout to identify bottlenecks in the performance of speed-based conflict resolution in a multilayered airspace structure. Results show that the current airspace structure and conflict detection and resolution concepts need to be refined to further reduce conflicts and intrusions that occur in constrained environments. First, additional measures must be adapted to further prevent conflicts during turning and merging. Second, conflict resolution manoeuvres must account for speed limits resulting in turn radii which do not cross physical boundaries. Finally, conflict detection needs to consider the topology of the streets to prevent false-positive conflicts and to prepare in advance for conflicts resulting from heading changes in non-linear streets. ... Read more

Driven by rising consumer demand, interest is growing in the application of autonomous unmanned aerial vehicles (drones) for the last-mile delivery of small express packages and fast-food meals in cities. To be realised, this would require the Very Low Level (VLL) urban airspace to be able to cope with high traffic densities of commercial delivery drones. The potential benefits of such novel drone-based applications are a reduction of traffic congestion in cities, lower greenhouse gas emissions and more efficient transportation operations. To help realise this concept, programs such as U-Space, the unmanned traffic management system for Europe, are developing important services such as deconfliction management and dynamic capacity management. However, for several of these services, design choices will depend on how, and how extensive they will be used. It therefore becomes important to estimate how many delivery drones would operate in a typical city. This paper aims to provide an estimate by establishing a framework to determine the traffic demand for express drone-based package delivery of five European countries. In addition, a detailed case-study is presented for determining traffic density of express package drone delivery for Paris metropolitan area in order to assess the feasibility from a user's perspective. The paper also discusses the potential of fast-food meal delivery drones compared to traditional delivery modes for Paris. Results suggest that hourly traffic densities culminating from express package and fast-food meal delivery drones will exceed today's global commercial aircraft traffic of 10,000 per day by more than six-fold for just one potential metropolitan city. ... Read more

The objective of this paper is to raise awareness about the significance of collecting and ensuring the quality of the obstacle data required for the safety of air navigation for both manned and unmanned aviation. This information could be of importance to geodetic, CityGML, 3D model and Building Information Management (BIM) community. With the advancement of future air mobility concepts such as drones and Personal Air Vehicles (PAVs), there is an increased demand for obstacle data of higher accuracy, including at Very Low Level (VLL) altitude. The paper presents the requirements pertaining to aviation such that the above mentioned communities could understand the existing complexity. This complexity adheres to the aggregation of quality-assured obstacle data from domains outside the aviation field’s responsibility. It is expected that with model developments (e.g. BIM), new solutions could be identified to support the aviation community with the aggregation of obstacle data of required quality. ... Read more

This paper describes the development of an optimization-based multi-stage centralized planning system for the efficient routing and assignment of extended flight formations in commercial airline operations. In an extended formation, where aircraft are longitudinally separated by 5-40 wingspans, a trailing aircraft can attain a reduction in induced drag at fixed lift, and consequently in fuel burn, by flying in the upwash of the leading aircraft’s wake. To organize the assembly of flight formations on a network-wide scale essentially two distinct approaches can be taken, viz., a centralized approach and a decentralized approach. Both approaches have distinct advantages and disadvantages. In this study a novel multi-stage method for flight formation assignment is proposed that combines the advantages of the decentralized approach (fast computation and reduced vulnerability to flight delays) with the main benefit of the centralized approach (a near-global optimum in terms of fuel savings). The multi-stage centralized approach that we propose is validated and subsequently demonstrated in a case study involving a wave of 267 eastbound transatlantic flights. In the case study fuel savings of 6.8% are recorded (relative to flying “solo”), while flying in formations comprising up to 16 aircraft. ... Read more

The concept of autonomous drone delivery in urban areas has gained a favorable amount of media attention over the past few years. Companies such as Amazon, Uber and Matternet are investigating the use of drones to transport parcels in order to solve the disaggregate delivery (last-mile) problem. This solution could potentially reduce vehicular congestion in cities by replacing traditional transport modes used in last-mile delivery, such as trucks, vans and bikes, with a fleet of autonomous drones flying in an urban airspace. To realize this concept, the design of an urban airspace for drones is necessary. However, the design of an urban airspace for drones will depend on critical design metrics such as drone traffic densities, traffic distribution patterns, distance between origin-destination, and the number of distribution centers. For this study, we first tackle the first metric, drone traffic density. This metric will provide an indication for the required urban airspace capacity and its expected demand. This paper therefore establishes a framework for determining the traffic density of delivery drones for a typical urban city airspace in Europe. In addition, the paper presents a cost-analysis study for fast-food delivery via drones relative to electric bikes. ... Read more

The work presented in this paper is part of the SESAR Horizon 2020 exploratory research project DREAMS, which analyses operational and technical aspects of drone Aeronautical Information Management (AIM) for Europe’s Unmanned Traffic Management system, U-Space. The main objective of DREAMS is to analyse the present and future needs of aeronautical information for future drone flight. The present paper investigates the required information services for achieving safe drone traffic operations in very low altitude airspace. The required drone information services were identified by conducting a comprehensive gap analysis on existing information services from manned aviation and current U-Space service providers in line with drone operator and user requirements. The latter was amalgamated from a comprehensive online survey, an identification of reference scenarios and high-level U-Space services. This research study indicated information gaps in seven key categories: flow management, meteorological, environment, flight, surveillance, communication and drone (vehicle) information. Finally, solutions to bridge these gaps are proposed in this paper. ... Read more