A Two-Echelon Covering Tour Vehicle Routing Problem with Drones for Post-Disaster Relief

A Two-Echelon Covering Tour Vehicle Routing Problem with Drones for Post-Disaster Relief

Dang Viet Anh Nguyen, Rajesh Piplani, Aldy Gunawan · N/A · 2026

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Summary

We introduce the two-echelon covering tour vehicle routing problem (2E-CTVRP) for the distribution of relief supplies after a disaster. In the first echelon, a fleet of trucks transports supplies and drones from a central depot to satellites at the periphery of the affected area.

Abstract Summary

We introduce the two-echelon covering tour vehicle routing problem (2E-CTVRP) for the distribution of relief supplies after a disaster. In the first echelon, a fleet of trucks transports supplies and drones from a central depot to satellites at the periphery of the affected area. In the second echelon, drones launched in parallel from the satellites deliver the supplies to the centroids of victim clusters, which are obtained by clustering the victim locations, and each truck waits at a satellite until its drones have returned. The problem combines the assignment of satellites to trucks, the sequencing of the truck routes, and the assignment of clusters to satellites, and minimizes the sum of the arrival times of the trucks at the satellites and at the depot. We formulate the 2E-CTVRP as a mixed integer linear program and propose a hybrid metaheuristic, GRASP-ILS-PR, which combines greedy randomized construction, a single-trajectory search, and periodic path relinking on the assignment of clusters to satellites. On a new benchmark set of 110 instances, GRASP-ILS-PR finds all known optimal solutions within 30 seconds, matches or improves on the one-hour solutions of a commercial solver on most larger instances, and improves on them by up to 11% for instances with 50 satellites. It clearly outperforms a conventional GRASP with evolutionary path relinking and yields more consistent results than a simulated annealing algorithm that uses the same search components. An analysis of two fleet configurations shows that few large trucks minimize the cumulative arrival time in most instances, whereas many small trucks deliver supplies to the victims earlier and more equitably in every instance.

Key Points

  • We introduce the two-echelon covering tour vehicle routing problem (2E-CTVRP) for the distribution of relief supplies after a disaster.
  • In the first echelon, a fleet of trucks transports supplies and drones from a central depot to satellites at the periphery of the affected area.
  • In the second echelon, drones launched in parallel from the satellites deliver the supplies to the centroids of victim clusters, which are obtained by clustering the victim locations, and each truck waits at a satellite until its drones have returned.
  • The problem combines the assignment of satellites to trucks, the sequencing of the truck routes, and the assignment of clusters to satellites, and minimizes the sum of the arrival times of the trucks at the satellites and at the depot.
  • We formulate the 2E-CTVRP as a mixed integer linear program and propose a hybrid metaheuristic, GRASP-ILS-PR, which combines greedy randomized construction, a single-trajectory search, and periodic path relinking on the assignment of clusters to satellites.

Literature review

The 2E-CTVRP is related to five streams of research: vehicle routing in humanitarian operations, two-echelon vehicle routing, truck–drone routing, covering tour problems, and routing under uncertainty in post-disaster settings. This section reviews these streams and positions the 2E-CTVRP relative to them.

Since the first applications of vehicle routing to humanitarian relief [ 31 ] , research on routing models for disaster operations has expanded steadily.

Literature review — A Two-Echelon Covering Tour Vehicle Routing Problem with Drones for Post-Disaster Relief
Figure 1 : Spatial distribution of victim locations forming distinct clusters, with the number in each red circle indicating the number of victim locations in the area following the 2025 flood in Thai Nguyen Province, Vietnam (source: https://thongtincuuho.org/ )

Problem description and mathematical formulation

The 2E-CTVRP addresses post-disaster humanitarian delivery through a coordinated two-echelon system. It is motivated by the 2025 flooding in Thai Nguyen Province, Vietnam, where severe rainfall submerged residential areas and destroyed critical road infrastructure.

The problem reflects situations in which displaced residents gather at evacuation points while damaged bridges and roads prevent trucks from reaching the affected communities.

Problem description and mathematical formulation — A Two-Echelon Covering Tour Vehicle Routing Problem with Drones for Post-Disaster Relief
Figure 2 : Illustration of a 2E-CTVRP solution

Proposed Algorithm

In the response phase of a disaster, routing decisions must be made under tight time constraints and may have to be revised as information on damage, road accessibility, and demand becomes available. Solution methods for the 2E-CTVRP should therefore provide high-quality solutions within short computation times.

The computational results in Section 5 show that the MILP formulation of Section 3 is solved to proven optimality within one hour only for instances with up to nine satellites.

Proposed Algorithm — A Two-Echelon Covering Tour Vehicle Routing Problem with Drones for Post-Disaster Relief
Figure 3 : Construction of list $A$ for two truck routes

Computational experiments

Since no benchmark instances exist for the 2E-CTVRP, we generate a new set of instances that reflects the spatial characteristics of victim locations after a disaster. The generator follows the approaches used for two-echelon vehicle routing problems [ 7 , 6 , 64 ] and for truck–drone routing [ 39 ] .

Victims tend to move to safer locations and form clusters within the affected area; these clusters are generated following Perboli et al. [45] . The affected area is a circle with a radius of 1000 distance units, corresponding to 10 km.

Computational experiments — A Two-Echelon Covering Tour Vehicle Routing Problem with Drones for Post-Disaster Relief
(a) N1 – Relocation (intra-route)

Impact of the truck fleet on relief operations

This section compares the two truck fleets with respect to three dimensions of humanitarian logistics: efficiency, efficacy, and equity [ 24 ] . The analysis uses the best solutions found by GRASP-ILS-PR for the 90 instances of the main set, which form 45 pairs of instances that differ only in the truck fleet.

Let $e_{i}=a_{i}+t^{\prime}_{i\sigma(i)}$ denote the time at which the demand of the centroid assigned to satellite $v_{i}$ is delivered, where $a_{i}$ is the arrival time of the truck at $v_{i}$.

Impact of the truck fleet on relief operations — A Two-Echelon Covering Tour Vehicle Routing Problem with Drones for Post-Disaster Relief
(b) N2 – Biased swap (intra-route)

Sources and Demonstrations

Figures are reproduced from Nguyen et al. See the full paper for experimental details and the project page, when the paper links one, for demonstrations and videos.

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