Major ridesourcing companies Uber and Lyft have promised all-electric fleets by 2030 in an effort to reduce their carbon footprint. To understand the additional impacts of this transition, researchers from Carnegie Mellon University (CMU) and the University of Michigan conducted life-cycle comparisons of battery-powered electric vehicle fleets to a gas-powered one, using real-world rideshare data and a novel agent-based model built in Julia for simulating ridesourcing services with high geospatial and temporal resolution. A paper on their work is published in the ACS journal Environmental Science & Technology.

They used the model and the data to estimate the life cycle air pollution, greenhouse gas, and traffic externality benefits and costs of serving rides based on Chicago TNC trip data from 2019 to 2022 with fully electric vehicles.

We estimate that electrification reduces life cycle greenhouse gas emissions by 40–45% (9–10¢ per trip) but increases life cycle externalities from criteria air pollutants by 6–11% (1–2¢ per trip) on average across our simulations, which represent demand patterns on weekdays and weekends across seasons during prepandemic, pandemic, and post-vaccination periods.

A novel finding of our work, enabled by our high resolution simulation, is that electrification may increase deadheading for TNCs [transportation network companies] due to additional travel to and from charging stations. This extra vehicle travel increases estimated congestion, crash risk, and noise externalities by 2–3% (2–3¢ per trip). Overall, electrification reduces net external costs to society by 3–11% (5–24¢ per trip), depending on the assumed social cost of carbon.

—Mohan et al.

Mohan et al.

Ridesharing apps are an increasingly popular way to travel around urban areas, especially for people without their own vehicles. But the cars and SUVs used in these situations drive more miles each year than a typical personal vehicle, contributing a higher proportion of greenhouse gases to the environment.

Previously, researchers calculated that rideshare companies’ carbon footprints could significantly decrease by fully electrifying their fleets. However, few studies have used real-world rideshare trip data in their estimates, or included additional assessments of air pollution and traffic impacts, from the switch.

Lead author Aniruddh Mohan and colleagues wanted to develop a method that evaluated the life-cycle costs and benefits for two battery-powered ridesource fleets and a gasoline-powered one.

The researchers collected simulated rides provided by three fleets: gasoline-powered, and electric-powered with either 40 kWh or 60 kWh battery packs. Then, they did a comprehensive estimate of the use-phase and life-cycle impacts of the trips made in the simulations. Combining these data, they assigned a monetary value to each trip, based on the assumed damage done by carbon emissions, negative health impacts and traffic-related issues.

The analysis indicated that electrified fleets had 40-45% lower greenhouse gas costs per trip compared to the gasoline-powered version. But the battery-powered electric vehicles were responsible for slightly higher air pollution from increased demand at local power plants for recharging purposes, as well as more ground-level particulates from tire and brake dust. They also were involved in more traffic problems, including crashes, congestion and noise, than the internal combustion option.

In the simulations, battery-powered vehicles, particularly the 40 kWh ones, needed more frequent and longer trips without passengers to get to recharging stations. Overall, a conversion to battery-powered electric rideshare fleets could reduce the costs to society by 3-11% per trip, depending on the cost assigned to greenhouse gas emissions, the researchers say. They conclude that these results are specific to Chicago, and cities with different power grids and street layouts could have different assessments from full electrification.

The authors acknowledge funding from Carnegie Mellon University’s Wilton E. Scott Institute for Energy Innovation.

Resources

• Aniruddh Mohan, Matthew Bruchon, Jeremy Michalek, and Parth Vaishnav (2023) “Life Cycle Air Pollution, Greenhouse Gas, and Traffic Externality Benefits and Costs of Electrifying Uber and Lyft” Environmental Science & Technology 57 (23), 8524-8535 doi: 10.1021/acs.est.2c07030