Chicago Transit Authority Bus Fleet Electrification

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Partnering with Gannett Fleming for Zero-Emission Fleet Planning & Modeling

Client: Chicago Transit Authority
Location: Chicago, Ill.

 

Challenge

As one of the two largest transit agencies in the U.S., the Chicago Transit Authority (CTA) regularly evaluates ways to increase sustainability and improve air quality. With 25 electric buses in its fleet, CTA wanted to determine the feasibility and financial impacts of transitioning to a fleet that runs entirely on electric power.

The Chicago City Council committed to electrifying its diesel bus fleet by 2040 in April 2019. As part of this commitment, the City of Chicago and CTA unveiled Charging Forward: CTA Bus Electricification Planning Report. This report serves as a first-ever roadmap for the next 18 years in transitioning the fleet to battery electric buses (BEBs) along with the facilities and supporting infrastructure.

CTA received its first grant funding from the Federal Transit Administration (FTA) in August 2022. The FTA awarded CTA $29 million in grant funding to purchase electric buses and other safety improvements.

Partnering with Gannett Fleming, GeoDecisions leveraged our geographic information systems (GIS) and geospatial data expertise with our Esri® platinum partnership to develop the route analysis and subsequent charger sequencing model for an overall electric bus conversion program.

Solution

Route Analysis

The goals of the route analysis were to determine:

  • The feasibility of the current and future electric buses to complete the existing City of Chicago bus routes.

  • The needed energy for bus charging.

GeoDecisions established a data flow to conduct various simulations operating on actual routes. The output from the simulations helped calculate the state of charge (SOC). Due to Chicago’s weather and geography, we included environmental factors such as temperature and topography. Leveraging the power of location in the simulations produced more accurate information to be tested against physical calculations:

  • Power demand from the drivetrain during acceleration, cruise, and deceleration.

  • Regenerative braking for on-route charging.

  • Additional auxiliary power demands to control the cabin for heating, cooling, and lights.

 
 

GeoDecisions analyzed every second of bus operation to determine the needed electric power and SOC.

 
 

Charger Sequencing Model

The goals of the charger sequencing model were to determine:

  • A bus garage strategy for BEB charging and service, including bus sequencing and lane assignments.

  • The required infrastructure to recharge the buses, including the number of fast and slow charging stations and peak electrical power load.

  • The minimum number of buses needed to ensure successful operation.

  • Effectiveness and manpower scheduling (including bus operators) to accommodate and charge bus movements within the garage.

GeoDecisions developed an algorithm to loop through each minute of each day of garage operation.

  • Block loop: handle buses entering and exiting operation.

  • Service loop: identify and maintain buses and fast charge.

  • Slow charging loop: categorize and slow charge buses.

  • Idle loop: account for remaining buses (either ready or waiting).

We further analyzed the data to determine peak demands for full fleet electrification, reduced fleet, and slow charging.

 

The key findings from the charger sequencing model will guide the next steps of the CTA bus fleet electrification planning, including intelligent bus-to-charging lane assignments.

 

Key Technologies

  • Python – Pandas Data Analysis Library

  • Amazon Web Services (AWS)

    • ­    SageMaker Compute Platform

    • ­    Jupyter Notebooks

    • ­    S3 Storage

  • Esri ArcGIS Pro

  • Esri ArcGIS Online

Key Takeaways

  • A comprehensive electrification strategy that serves as a roadmap for the next 18 years to replace diesel buses with BEBs.

  • Inclusion of location information to strengthen decision-making and enhance data analysis of critical infrastructure improvements.

  • A complete route analysis that evaluated power demand and additional needed electricity.

  • A charger sequencing model to determine the best charging strategy and optimize the electrification process of the CTA bus fleet.

 

Learn more about Gannett Fleming’s role in the Zero-Emission Fleet Planning for the Chicago Transit Authority (CTA) project profile.