Toward greener transit: Carbon-efficient density thresholds for public transit vs. private vehicles

IF 7.3 1区工程技术 Q1 ENVIRONMENTAL STUDIES

Transportation Research Part D-transport and Environment Pub Date : 2025-02-11 DOI:10.1016/j.trd.2025.104641

Bumsoo Lee , Sungwon Lee

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引用次数: 0

Abstract

Despite its potential as a sustainable transportation mode, public transit in many low-density urban and suburban areas in the U.S often generates more CO₂ emissions per passenger-mile than privately operated vehicles (POVs), primarily due to low ridership and passenger loads. Using Gradient Boosting Decision Trees (GBDT) and spline regression models, this study investigates the non-linear relationship between population density and the relative carbon efficiency of transit compared to POVs across the 136 largest U.S. urban areas. This study found that the minimum density required for public transit to be more carbon-efficient than driving, while controlling for other factors, is around the lowest 10th percentile of population-weighted density (PWD)—approximately 3.4 persons per acre. Further, a critical density threshold was identified at around the 80th percentile of PWD, about 8.6 persons per acre, beyond which the positive impact of population density on transit’s carbon efficiency significantly shifts up.

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来源期刊

Transportation Research Part D-transport and Environment 工程技术-运输科技

CiteScore

14.40

自引率

9.20%

发文量

314

审稿时长

39 days

期刊介绍： Transportation Research Part D: Transport and Environment focuses on original research exploring the environmental impacts of transportation, policy responses to these impacts, and their implications for transportation system design, planning, and management. The journal comprehensively covers the interaction between transportation and the environment, ranging from local effects on specific geographical areas to global implications such as natural resource depletion and atmospheric pollution. We welcome research papers across all transportation modes, including maritime, air, and land transportation, assessing their environmental impacts broadly. Papers addressing both mobile aspects and transportation infrastructure are considered. The journal prioritizes empirical findings and policy responses of regulatory, planning, technical, or fiscal nature. Articles are policy-driven, accessible, and applicable to readers from diverse disciplines, emphasizing relevance and practicality. We encourage interdisciplinary submissions and welcome contributions from economically developing and advanced countries alike, reflecting our international orientation.