Exact Models (MIP)
Mixed Integer Linear Programming Formulations
These papers describe arc flow decision variables, flow conservation constraints, sub-tour elimination, and time window coupling across tiers.
Mathematical Formulations for Two-Echelon Routing
Mehmet AnΔ±l Akbay, Christian Blum (Artificial Intelligence Research Institute, CSIC)
Presents various compact and extended formulations for two-echelon routing, comparing 2-index vs 3-index models, and details time window coupling between tier 1 and tier 2.
Last-mile delivery concepts: a survey from an OR perspective
Nils Boysen, Stefan Fedtke, Stefan Schwerdfeger
The most exhaustive survey on two-tier logistics networks: analysis of urban micro-hubs, vehicle synchronization, and fixed fleet cost vs. distance cost trade-offs.
Heuristics & Practical Solving
Solving Real-Scale Instances
On large instances (dozens of customers and hubs), exact MIP solvers hit computational limits. ALNS (Adaptive Large Neighborhood Search) metaheuristics produce near-optimal solutions in seconds.
A Large Neighbourhood Based Heuristic for Two-Echelon Routing
Ulrich Breunig, Verena Schmid, Richard F. Hartl, Thibaut Vidal
Details ruin-and-recreate operators (Shaw removal, Random removal, Worst removal) and insertion operators (Greedy, Regret-k) applied simultaneously on tier 1 and tier 2 routes.
The Electric Two-echelon Vehicle Routing Problem
Ulrich Breunig, Roberto Baldacci, Richard F. Hartl, Thibaut Vidal
Models situations where Tier 1 uses heavy diesel trucks and Tier 2 uses light electric vehicles with battery range and recharging duration constraints.
Bibliographical Synthesis
Recent Literature Reviews
Comprehensive overview papers surveying classifications and benchmark problems in multi-tier logistics.
Two-echelon Parcel Delivery: A Literature Review
Nima Moradi, Niloufar Mirzavand Boroujeni, Navid Aftabi, Amin Aslani
Review focused on urban parcel delivery networks with intermediate transfer hubs and strict time windows.
π Read local PDF (37 pages) βLarge-Scale Two-Echelon Location Routing Problems
Optimization & Operations Research Community
Decomposition algorithms and scalable mathematical heuristics to solve complex distribution networks with hundreds of delivery points and dozens of intermediate depots.
π Read local PDF (40 pages) βExtensions & Complex Scenarios
Drones, Disaster Relief & Robustness
Advanced real-world applications combining heavy freight, delivery drones, or humanitarian emergency logistics.
Two-Echelon Routing with Truck and Drones
Minh HoΓ ng HΓ , Lam Vu, Duy Manh Vu (arXiv:2004.02275)
Heavy trucks transport goods to intermediate launch sites (Tier 1), then an autonomous fleet of drones performs last-mile deliveries with customer time windows (Tier 2).
π Read local PDF (29 pages) βTwo-Echelon Routing for Post-Disaster Logistics
Tasnim Ibn Faiz, Chrysafis Vogiatzis, Md. Noor-E-Alam (arXiv:2001.06456)
Multi-tier emergency routing under strict time horizons for rapid relief distribution following natural disasters.
π Read local PDF (38 pages) β