How Does Eco-Routing Affect Total System Emissions? City Network Predictions From User Equilibrium Models

TL;DR

This paper investigates how eco-routing, where vehicles choose routes to minimize emissions, can paradoxically increase overall emissions due to congestion effects, demonstrated through models and real city network data.

Contribution

It introduces a multiclass user equilibrium model incorporating eco-routing and reveals the existence of the Braess paradox in this context, with empirical city network analysis.

Findings

Eco-routing can increase total emissions in some scenarios.

The Braess paradox applies to eco-routing in city networks.

Empirical data shows eco-routing may worsen emissions in real networks.

Abstract

Transportation contributes a substantial fraction of all greenhouse gas emissions. One approach for reducing such emissions is to modify vehicles' route choices to minimize their fuel consumption or emission, which is known as eco-routing. Most eco-routing is based on vehicles choosing routes that minimize their individual fuel consumption or emissions. The Braess paradox demonstrates that when vehicles choose routes to minimize their individual goals, the aggregate effect may paradoxically result in the opposite net effect due to changes in congestion patterns. We construct a multiclass user equilibrium model in which some vehicles use eco-routing and others seek to minimize their individual travel times. Using this model, we show that the Braess paradox exists for eco-routing. If a large number of vehicles are trying to minimize their fuel consumption or emissions, the total fuel consumption or emissions may increase. We then solve the multiclass user equilibrium on publicly available city network data, and find that eco-routing results in increases in fuel consumption and emissions on some city networks as well.