A Triangulated Spatial Index for Quantifying Real-World Freight Emissions Discrepancies

• Abey Litty

  Texas University

  Author

Road freight transport accounts for a substantial and growing share of global greenhouse gas emissions, yet the tools used to quantify these emissions systematically diverge from real-world conditions. Certification-based emission factors (CEFs) derived from standardized test cycles and activity-based calculation frameworks such as the GLEC Framework and ISO 14083 provide operational estimates, but their accuracy is compromised by methodological flexibility, sparse spatial resolution, and the exclusion of operational variables including payload variability, engine load dynamics, and route-specific congestion. This study develops and validates a Triangulated Spatial Index (TSI) that integrates GPS trajectory data, portable emissions measurement system (PEMS) observations, and spatial clustering algorithms to quantify and visualize discrepancies between calculated and observed freight emissions at the road-segment level. Using a dataset of 18,432 heavy-duty truck trajectories and 214 PEMS validation runs across a mixed urban-freeway freight corridor, the TSI achieved 89.4% agreement with PEMS-measured emissions for NOx and CO₂, outperforming GLEC-based activity calculations by 34.7 percentage points. The framework is operationalized through a modular system design that follows the triangulation principles established in Okeke and Rahim (2026) and applies the construct validation logic of Okeke (2026) to environmental measurement. The TSI provides a replicable methodology for municipalities, port authorities, and logistics operators to identify emission hotspots, prioritize mitigation investments, and report emissions with greater spatial and operational fidelity than current regulatory frameworks permit.

• pdf

Copyright (c) 2026 Abey Litty (Author)

This work is licensed under a Creative Commons Attribution 4.0 International License.