Understanding the scaling of transport energy use with operational density
File(s)
Published version
Author(s)
Anupriya
McCoy, Emma
Graham, Daniel J
Type
Journal Article
Abstract
Given the substantial contribution of transport operations to global energy demand, enhancing their
energyefficiencyiscrucial for sustainable urbanmobility. Thisstudy investigateswhether intensifying
the use of fixed transport networks, termed operational densification, reduces energy consumption.
Grounded in economic theory, we develop a novel causal model to estimate the energy impacts of
densification across two major commuting modes: urban rail transit (metro) and private car travel.
Using a unique panel dataset of 27 metro operations worldwide, we find that a 10% increase in
passenger-kilometres travelled on a fixed network reduces energy use per passenger-kilometre by
3.45%.Thesegainssurpass whatkineticenergy principles alone predict, as fixed energy inputs such
asinfrastructure and maintenance are distributed across increased usage. In contrast, analysis of the
Millennium Cities Database reveals no significant energy savings from densification in private car
travel, likely due to limited shared infrastructure or operational scale economies.
energyefficiencyiscrucial for sustainable urbanmobility. Thisstudy investigateswhether intensifying
the use of fixed transport networks, termed operational densification, reduces energy consumption.
Grounded in economic theory, we develop a novel causal model to estimate the energy impacts of
densification across two major commuting modes: urban rail transit (metro) and private car travel.
Using a unique panel dataset of 27 metro operations worldwide, we find that a 10% increase in
passenger-kilometres travelled on a fixed network reduces energy use per passenger-kilometre by
3.45%.Thesegainssurpass whatkineticenergy principles alone predict, as fixed energy inputs such
asinfrastructure and maintenance are distributed across increased usage. In contrast, analysis of the
Millennium Cities Database reveals no significant energy savings from densification in private car
travel, likely due to limited shared infrastructure or operational scale economies.
Date Issued
2025-09-01
Date Acceptance
2025-08-01
Citation
npj Sustainable Mobility and Transport, 2025, 2 (1)
Publisher
Springer Science and Business Media LLC
Journal / Book Title
npj Sustainable Mobility and Transport
Volume
2
Issue
1
Copyright Statement
©TheAuthor(s) 2025. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproductionin any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
License URL
Identifier
10.1038/s44333-025-00057-1
Publication Status
Published
Article Number
39
Date Publish Online
2025-09-01