A Mixed-Integer Framework for Sustainable, Service-Aware Vehicle Routing in Heterogeneous Fleets

Tiryaki, Fatih; Tuna, Yusuf Mert; Qadri, Syed Shah Sultan Mohiuddin

doi:10.22034/ISS.2026.10242.1074

A Mixed-Integer Framework for Sustainable, Service-Aware Vehicle Routing in Heterogeneous Fleets

Document Type : ODSIE 2025

Authors

Fatih Tiryaki

Yusuf Mert Tuna

Syed Shah Sultan Mohiuddin Qadri

Industrial Engineering Department, Engineering Faculty, Çankaya University, Ankara, Turkey

10.22034/ISS.2026.10242.1074

Abstract

Objective: This paper develops a practical vehicle routing model that embeds environmental and service-quality considerations into a single cost-minimization framework.
Methods: The formulation captures realistic operations by modeling a heterogeneous fleet with type-specific capacities, fuel consumption, and emission intensities, incorporating soft time windows and an explicit, auditable aggregate emission cap. The mixed-integer program is solved via CPLEX. Parameter sensitivity is assessed using a computationally efficient Taguchi L9 (3³) orthogonal array. Furthermore, the model's scalability and robustness are validated using adapted Solomon benchmark instances (e.g., C101) with synthetic fleet heterogeneity.
Results: ANOVA results reveal a dual-dominance structure: emission penalties primarily govern economic costs, while tardiness penalties dictate operational decisions, fleet expansion, and total emissions. Benchmark validations confirm that the exact formulation effectively scales across different network topologies and problem sizes.
Conclusion: The proposed framework successfully bridges the gap between theoretical green routing and policy-driven logistics. It provides managers with actionable strategic corridors to balance strict punctuality requirements against emerging carbon regulations, utilizing the model as a "digital twin" for optimal fleet allocation.

Keywords

vehicle routing problem (VRP)

sustainable logistics

heterogeneous fleet

emission penalty

time windows

Taguchi L9

Subjects

Transportation, Distribution and Routing

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