Charging Forward
CTA Bus Electrification Planning ReportFebruary 2022

Chicago Transit Authority

Table of Contents
Letter from CTA President Dorval Carter						

4Glossary of Terms								

6Acknowledgments								

7Map of CTA Bus Garages and Routes						

8Executive Summary								

9Chapter 1. Overview of Electric Bus Technologies					

16

Focus: Hydrogen Fuel Cell Electric Buses					

19Chapter 2. Initial Fleet Electrification Analyses					

202a. Bus Purchasing Timelines							

212b. Equity Analysis 								

222c. Schedule Compatibility Analysis						

25Focus: Red Line Extension Coordination 					

282d. Garage Charging Strategies						

292e. Facility Upgrade Needs 							

34Chapter 3. Defining Detailed Electrification Scenarios 				

39Focus: CTA Bus Fleet Size in the Broader Contexts of
Climate Change, Equity, and COVID-19
				

45

Chapter 4. Cost and Emissions Projections of Electrification Scenarios		

47

Focus: Grant Funding for Electric Bus Program 				

56Chapter 5. Conclusions								

57Chapter 6. Next Steps 								

63Appendix
Section A. Detailed Results of the Equity Analysis					

A1Section B. Detailed Assumptions for Schedule Modeling				

A4

Section C. Detailed Assumptions for Modeling of Garage Charging			

A8

Section D. Detailed Assumptions and Inputs for Fleet Electrification Cost Modeling A11

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List of Figures and Tables
Figure 1 – Timeline of major steps towards CTA bus fleet electrification to date			Figure 2 – Example timelines for transitioning the CTA bus fleet and upgrading CTA bus facilities
Figure 3 – Summary of three sets of technology assumptions that were used for analyses		
Figure 4 – Photo of pantograph charger at Navy Pier						Figure 5 – Flow chart illustrating overall study approach					Figure 6 – Graph of potential CTA bus fleet transition timeline					Figure 7 – Map of the CAQHI index throughout Chicago					Figure 8 – Map of proposed new Red Line Extension						Figure 9 – Conceptual illustration of potential garage charging operations that were evaluated		Figure 10 – Different combinations of slow charging and fast charging are possible at garages		
Figure 11 – Graph comparing bus assignments and design capacity at garages			
Figure 12 – Potential Timeline of Garage Upgrades						Figure 13 – Projected annual costs comparing average results for electric scenarios (left) andaverage results for diesel scenarios (right)							Figure 14 – 2022-2040 Capital costs compared between scenarios				Figure 15 – 2040 Operating costs compared between scenarios				Figure 16 – 2041-2048 Average annual capital costs comparison				Figure 17 – Projected emissions of three pollutants under diesel scenarios and electrification scenarios

Table 1 – Ratings of CTA bus garages based on minority and low-income populations neareach garage and its associated routes							Table 2 – Ratings of CTA bus garages based on the CAQHI scores near each garage and its
associated routes									Table 3 – Percent of Fall 2018 vehicle blocks compatible with electrification under
different daily schedules, on-route charger networks, and technology levels			
Table 4 – Example analysis results from 74th Street Garage					Table 5 – Classification of facility upgrades						Table 6 – Summary of eight fleet conversion scenarios					Table 7 – Recommended sequencing of bus garages with the factors that were considered		Table 8 – Summary of eight fleet conversion scenarios including the fleet growth that can beaccommodated									Table 9 – Major cost categories included in cost modeling					Table 10 – Summary of cost modeling results for the period 2022-2040 				CHARGING FORWARD | CTA BUS ELECTRIFICATION PLANNING REPORT

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Letter from CTA President
Dorval Carter
Dear Fellow Chicagoans,
For more than a century, public transit has been oneof the most sustainable modes of transportation,lesseningtheenvironmental

footprintofthetransportation sector by reducing personal car trips
and supporting sustainable land use development.
Over the last few years, public transit has gotten evermore environmentally friendly with the emergenceof electric buses—which will further reduce healthimpacting tailpipe emissions and climate-changing
greenhouse gas emissions.
I am proud to present to you Charging Forward, the culmination of a comprehensive strategic planningstudy which sets a course for full electrification of the Chicago Transit Authority’s (CTA) entire bus
fleet by 2040.
CTA has been at the forefront of the shift to electric bus technology since our first two electric buses
entered service in 2014, making us one of the first transit agencies in the country to run electric busesin revenue service. Today, we have eight electric buses in service, and 17 more that are being tested forservice at our garages—altogether we expect to have 25 electric buses in service by the middle of 2022. To
date, CTA has also secured more than $130 million in grant funding to continue expanding our electric bus
fleet and installing the needed charging infrastructure.
Electrifying the CTA bus fleet will produce an array of community benefits:• CTA will lead by example, contributing to cleaner air and less traffic noise. These benefits areespecially important in communities that bear an inequitable burden of air pollution today, resulting
in higher rates of asthma and other health effects. These are the areas where we are prioritizing
our electric bus deployments.
• Public transit already produces less than half the CO2 emissions that driving does per passenger
mile.1 Converting from a diesel to an electric bus fleet will reduce the greenhouse gas emissions
from buses even further.

1 Quantifying Greenhouse Gas Emissions from Transit. American Public Transportation Association, 2018.
An Update on Public Transportation’s Impacts on Greenhouse Gas Emissions. Transit Cooperative Research Program, 2021.
CHARGING FORWARD | CTA BUS ELECTRIFICATION PLANNING REPORT

4• Electric buses are expected to create operational savings and benefits for CTA including fuelcost savings and improved price stability.
• With one of the biggest bus fleets in the nation, CTA’s adoption can help drive advances in electricvehicle technology, especially for heavy-duty vehicles.
Equity considerations have been critical priorities as CTA has identified the initial routes and garages forelectric buses, leading to early deployments on the South and West Sides of Chicago. The electric buses
CTA operates currently are based primarily at Chicago Avenue Garage and operate on route #66 serving
Chicago Avenue. Charging infrastructure is also installed at 74th Street Garage to support new electric bus
deployments in 2022. The additional grants we have secured are anticipated to fund more electric buses
for deployment on route #66, and additional buses and chargers to be deployed at CTA’s 103rd Street
Garage, where many South Side routes originate.
As proud as I am of the progress we’ve made, it is clear that we have a long way to go. Our fleet includes
more than 1,800 buses that will need to be replaced. They are housed at seven bus garages and served
by a heavy maintenance facility—all of which will need to be substantially upgraded and retrofitted withcharging infrastructure to make electrification a reality. This is no small undertaking and requires thecareful coordination of many interrelated investments.
This report summarizes the findings of key analyses that will inform our strategic direction on major decision
points and establishes a practical framework for CTA to advance towards full electrification. It gives us
important guidance on which technologies to invest in, where to install charging infrastructure, how tosequence the electrification of garages and routes, and how to ensure that the related facility upgrades arecoordinated with other modernization needs to maximize cost effectiveness and overall system reliability.
Simply put, this report is the roadmap to our bus future.
With the completion of Charging Forward, CTA is well-positioned to compete for funding, advocate forpolicies, and drive technology advances that will be essential to implement this plan. Electrifying the CTA
bus fleet by 2040 is a complex and challenging undertaking, but together – with support from you andother stakeholders, as well as proper funding – it is possible. We are fully committed to reaching thisimportant goal for our city and our region.
Dorval Carter

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Glossary of Terms
Electric bus – a bus powered by an onboard battery that drives an electric motor,
also called a “battery electric bus.” For the purposes of this report, the term does notinclude buses powered by hydrogen. Note that hydrogen fuel cell buses may also be
considered electric buses in some contexts because the fuel cells use hydrogen to
generate electricity, which then powers the bus’s drivetrain.
Slow charger – an electric bus charger providing less than 250 kilowatts (kW) of
power, typically used for charging buses while they are parked overnight at garages.
Fast charger – an electric bus charger providing greater than 250 kW power, which
may be used for on-route charging or for quickly charging buses at garages.
On-route charging – the practice of charging electric buses at the endpoint of a route(which may also be called a terminal or layover location) during the time that the bus
is scheduled to wait before starting its next trip.
Vehicle block – an assignment of work for a single (non-specific) bus, outlining all
trips, both revenue and non-revenue, and any recovery time between those trips. A
vehicle block typically starts and ends at a garage, but some have alternate start/end
locations.
Standard Bus Equivalent (SBE) – a measure of bus storage capacity, in which astandard 40-foot bus is counted as 1 SBE and an articulated 60-foot bus is counted
as 1.5 SBE.
State of Charge (SOC) – the percent of a battery’s capacity that remains charged withuseable energy; if a vehicle’s battery SOC dips below a certain threshold, it is at riskof failing to operate.
Pantograph – a movable mechanical arm located over a bus that is used to convey
an electrical connection between a charger and an electric bus so that power can betransferred.
Gantry – an overhead structure that is used to support equipment such as charging
pantographs.

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Acknowledgments
This study was made possible through the generous support of the Joyce Foundation,and in collaboration with Civic Consulting Alliance. We thank them for their partnershipin this process.
The study was conducted by Sam Schwartz Consulting in close consultation with CTA
staff.

Timeline of major steps towards CTA bus fleet electrification

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Figure 1 – Timeline of major steps towards CTA bus fleet electrification to date

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Map of CTA Bus Garages and Routes

This map identifies CTA’s seven bus garages
and their associated bus routes. If a route isoperated out of more than one garage, it isassociated with the garage that operates thegreatest portion of service for the route.
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Executive Summary
Charging Forward describes analyses that inform the major decisions
that comprise CTA’s bus fleet electrification strategy. These include
assessments of equity and environmental justice factors, modeling
electric bus technology performance with current bus schedules, andtesting different approaches to charging buses on-route and at garages.
The analyses also include identifying existing infrastructure upgradeneeds, projecting costs over the transition timeline, and estimating
emissions reductions. The summary-level findings of these analyses aredescribed below.

Equity and Geographic Sequence
Compared to diesel buses, electric buses emit less local air pollution that is harmful
to public health, which is particularly important in neighborhoods on Chicago’s Southand West Sides, where populations with health-related vulnerabilities represent agreater portion of residents and where air quality is often worse.2 Because of this, CTA
plans to prioritize the electrification of bus routes and garages serving these areas.
The planned sequencing of garages, shown in the timeline graphic on page 12, places
primacy on equity and environmental justice considerations.

Technology Compatibility with CTA Bus Schedules
Modeling of current bus schedules showed that, with the electric bus technologythat CTA is already using and a limited network of on-route charging locations, about
66% of CTA’s weekday service could be reliably completed by an electric bus. Electric
bus technology is rapidly improving, however, so we also modeled different levels oftechnology improvement, which showed that CTA could reasonably expect to achieve
around 88% compatibility for the same schedules based on technology improvement
alone. The remaining portion of service would likely require other changes, and the

2 Based on a review of the Chicago Air Quality and Health Index (CAQHI) developed by the Chicago Departmentof Public Health: www.chicago.gov/city/en/depts/cdph/provdrs/healthy_communities/svcs/air-quality-andhealth.html

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options for electrifying the longest vehicle blocks3 haveimportant tradeoffs, discussed further in Chapter 2c.

Locations of Electric Bus Chargers
Analysis of different networks of chargers, with different
levels of on-route charging available, concluded thatthe best approach for CTA is to centralize charging ofelectric buses at bus garages to the greatest extent
feasible, and construct a limited number of on-routechargers at key bus layover locations in order tosupplement garage charging and extend the mileage
range where most needed.

Garage Charging Technologies andOperations
At garages, buses could charge their batteries
either using “slow chargers” where they are parked
overnight, or using “fast chargers,” which can charge
buses relatively quickly before they are parked for thenight, more similar to current diesel fueling operations.
Slow chargers would likely take up more space thanfast chargers, which could exacerbate existing garage
capacity issues. They are also more expensive thanfast chargers on a “per bus” basis. However, utilizing
more fast charging could require more operational
complexity and could require more labor to movebuses to and from chargers. Fast charging is also
relatively untested on a large scale, and there areconcerns that it may lead to faster battery degradationcompared to slow charging and might raise reliability
issues particularly for electric buses stored outside
in cold weather. As a result, this analysis concluded
that a mixture of fast charging and slow charging at
each garage is likely best, with more fast charging
recommended if that technology performs well.
3 Vehicle blocks represent the daily assignment of work for a single(non-specific) vehicle, including all trips, both in-service and out-ofservice.
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Facility Needs
CTA’s fleet of more than 1,800 buses is housed
and serviced at seven bus garages and one heavy
maintenance facility. All eight of these facilities will need
new charging infrastructure and other upgrades in order
to electrify the full fleet. These investments are every
bit as important as the electric vehicles themselves;
without sufficient charging infrastructure and thepower supply to feed it, electric buses cannot provide
service. Many of these facilities also have significant
existing state of good repair needs that will need tobe addressed or accelerated as part of electrification.
New equipment may have physical impacts that trigger
code requirements, prompting additional work (suchas fire/life safety code). Conditions discovered in thecourse of implementation may necessitate additional
repairs. Other facility upgrades may be advisable
in order to help protect the investment in electric
infrastructure or efficiently stage work and avoid
duplicating effort. For example, if we are installingcharger equipment and the surrounding pavement
needs replacement, it makes sense to do this at thesame time, and any building envelope and roof repairs
should be done before or simultaneous to installationof new equipment within garage buildings. CTA’s bus
garages also already have a significant capacity deficit
today, meaning that more buses are currently housed
at the garages than they were designed to support. The
existing need for an additional bus garage will become
more pressing as electrification will likely require more
space for charging infrastructure and daily operations.
All of these bus facility improvements require carefulassessment, planning, design and coordination toensure they are completed in the appropriate orderand avoid major disruptions to daily operations.

CHARGING FORWARD | CTA BUS ELECTRIFICATION PLANNING REPORT“Without sufficientcharging
infrastructure andthe power supply
to feed it, electricbuses cannot provide
service.”11Key Components of Electrification Timeline
The specific steps in CTA’s electric bus implementation timeline will vary based on
the performance and evolution of technology, and the degree to which CTA may needto grow its service over the transition period, but the key features of electrification
timelines are common among all the scenarios we developed for further analysis:• Based on a standard bus lifetime of 14 years, CTA’s bus purchases will have totransition to all-electric by 2026 to ensure that the last diesel buses are retiredby 2040.
• Facility upgrades will need to be timed to accommodate the number of electricbus purchases planned for each year, and to minimize overlap between the
more significant projects.
Electric
Non-electric

Potential Timeline for Transition of CTA Bus Fleet
100%

Portion of Bus Fleet

90%
80%
70%
60%
50%
40%
30%
20%

Potential Timeline of Facility Upgrades

2040

2039

2038

2037

2036

2035

2034

2033

2032

2031

2030

2029

2028

2027

2026

2025

2024

2023

0%

2022

10%

Planning/Concept Design
Implementation
Infrastructure in place to supportscaling up electric buses

Chicago
103rd
77th
South Shops
74th
New Garage
KedzieForest Glen

2040

2039

2038

2037

2036

2035

2034

2033

2032

2031

2030

2029

2028

2027

2026

2025

2024

2023

2022

North Park

Figure 2 - Example timelines for transitioning the CTA bus fleet and upgrading CTA bus facilities.

CHARGING FORWARD | CTA BUS ELECTRIFICATION PLANNING REPORT12• The order in which facilities are upgraded is based on equity considerations
and the need to space out major construction projects.
• Continued electrification of Chicago Avenue Garage and partial electrificationof 103rd Street Garage are anticipated over the 2022-26 period.
• Significant modernization will likely be required at CTA’s oldest bus facilities inorder to accommodate bus electrification. The first of these would be at 77th
Street Garage, planning for which will need to begin in 2022.
• The later years of the transition would have more sizeable electric bus
purchases and facility upgrade needs, including construction of a new garage
by 2032 and the significant modernization of two additional garages between
2035 and 2038.

Costs for Bus System Electrification
To help test different mixes of fast and slow charging across different levels of facility
investments, eight detailed electrification scenarios were developed and modeled,using our best estimates of the component costs involved. The modeling estimatedthat converting the fleet to electric buses would require an increase in capital funding
over the 2022-2040 transition period of $1.8 to $3.1 billion on top of the base costto maintain the existing bus fleet and facilities, which today is not fully funded. Thisestimate is based on the following:• Increased capital costs to purchase electric buses include only theincremental cost to purchase an electric bus instead of a diesel bus. This isbased on the additional existing cost for an electric bus over a diesel bus,
as well as a modest contingency and escalation factors to reflect the yearof expenditure. It also assumes that CTA replaces all buses at 14 years as abaseline scenario (which current funding levels have not allowed).
• New capital costs for electrification of facilities include installation of fast
chargers and slow chargers in the garages and the associated electricalupgrades to the garages (based on the charger scenario). Each facility
electrification scenario also includes the same assumption for on-routechargers at 13 locations.
• Capital costs for state of good repair facility upgrades and modernization
are not included in this estimate of increased capital costs for bus
electrification. These costs are discussed more in Chapter 2e, but arechallenging to parse with respect to electrification. Some facility upgrades

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and modernization will be required for the bus
electrification scenarios to be implemented.
Other facility needs may be programmed inconjunction with the electrification work to
optimize for efficiency, but some may not be
required specifically to support electrification.
Separate facility-specific analyses are required
to identify these needs and will also identify
opportunities to program state of good repair
needs, in coordination with the CTA’s Transit
Asset Management Plan targets.
• Capital costs for a new bus garage are notincluded in this estimate of increased capitalcosts. CTA bus garages already operateover capacity, and electrification scenarios
create further strain on available space andoperations. A new bus garage is likely to cost an
additional $450 million beyond the increased
capital funding needs identified above.
Electrification is expected to yield operating costsavings due primarily to the lower cost of electricity
compared to diesel fuel, which will increase as theelectric fleet grows, but these savings will not fully
offset the capital investment needed during thetransition period.
Our analysis indicates that the 2040 deadline forbus fleet electrification is feasible, but only if CTA
can secure significant additional capital funding. The
historic average funding of approximately $65 million
per year is woefully inadequate to cover the baseline
cost for bus replacement at 14 years and does not
begin to cover the costs for electrification (vehicles
and facilities), the additional garage upgrades andmodernization that will be necessary, or the new
garage.

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While existing electric bus grants can be used to make progress on less complex
charger installation and garage electrical upgrades, as well as purchasing additional
electric buses, funding for concept design and facility analyses for each of the garages
is an urgent near-term need. Each of the garages requires an analysis, and the oldest
facilities (77th Street, South Shops, Forest Glen and North Park) will require more
extensive modernization plans. Planning, site identification and environmental
analysis will need to start within the next two years for the new garage. In addition tonear-term planning funds, a reliable funding stream for implementation will be needed
to meet the 2040 commitment. This will need to include local and state funding to
supplement and match the increased federal funding for competitive Low- and NoEmissions Grants, Congestion Mitigation and Air Quality (CMAQ) Grants, and Bus &Bus Facility State of Good Repair Grants programs.

Environmental Benefits of Bus System Electrification
Finally, we quantified and modeled the environmental benefits of electrification interms of both the local “tailpipe” emissions and the total emissions inclusive of thoseoccurring at the power generation source. We found that full electrification of CTA’s
bus fleet is estimated to reduce total annual CO2e emissions from CTA buses by 73%,4
total NOx emissions by 98%, and local PM2.5 emissions by over 99%, compared withmaintaining a diesel fleet. It is worth noting that electrification is projected to increase
total PM2.5 emissions as a result of power generation, but this could be reduced if themix of power generators on the regional grid shifts toward cleaner energy sources.

Taken together, the results of the Charging Forward analyses show thatthe benefits of electrification will be significant, and also that a great dealof coordination and support from partner agencies and elected officials
will be needed to make this ambitious plan a reality.

4 Carbon dioxide equivalent, or CO2e, is a metric that combines the emissions from various greenhouse gases
based on their global warming potential.
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Chapter 1. Overview of Electric Bus
Technologies
Electric bus technologies have been rapidly improving in recent years,
and are expected to continue to do so.5 CTA’s first electric buses, deliveredin 2014, have batteries with 300 kilowatt-hours (kWh) of energy capacity.
CTA’s most recent electric buses have batteries with 440 kWh of energy
capacity, and models on the market today have even larger batteries with
660 kWh of energy capacity. Other associated technologies, including
charger equipment, have been improving along a similar trajectory. In
general, this is good news, but the rapid change also poses a challenge
for long-term planning. In order to help manage the uncertainty, wedeveloped several sets of technology assumptions for modeling andanalysis purposes.

Technology Assumptions
Assumptions were developed to account for the need for reliable performance, basedon reasonable but conservative expectations for technology. Figure 3 below shows thethree sets of assumptions that were developed and used throughout our analyses—
current technology, moderate improvement, and significant improvement—along withthe respective mileage ranges that can be reliably expected from a 40-foot electricbus for each. “Current technology” reflects the technology found in CTA’s most recent
electric bus purchases; “moderate technology improvement” is newly available on themarket, and “significant technology improvement” is likely to be available within the
fleet transition period.
Figure 3 – Summary of three sets of technology assumptions that were used for analyses      
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Note: “Effective ranges” are given for a fully charged 40-foot bus with midlife battery degradation during winterconditions.
5 Charging Forward focuses on battery electric bus technology, but we should note that other emissionsreducing technologies, such as hydrogen fuel cell buses, discussed further on p.19, may also be considered as anadditional solution in the long term as technologies and supply chains develop.

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16

All three technology levels incorporate detailed
assumptions that can be found in Section B of the
Appendix. These include factors that a) reduce thebattery capacity to reflect midlife battery degradation
and usability limits, b) apply an energy consumption
rate that reflects performance during winter conditions,and c) reflect that batteries do not always accept thefull power from chargers (particularly at the high andlow SOC values). Note that the battery and charger
technology assumptions apply to both 40-foot and
60-foot buses, but the mileage range for 60-foot buses
is approximately 23% lower due to the higher battery
consumption rate needed to power a heavier vehicle.

Charging Solutions
The two standard mechanisms for charging electricbuses are plug-in charging and overhead charging.
Plug-in charging has been common for small-scale
deployments, but it has the disadvantage that staff
must manually plug and unplug buses every time
charging occurs. In contrast, overhead charging canoccur in a largely automated fashion with minimal staff
effort required; with this system, a pantograph candescend when a bus is properly positioned to begin
charging, as illustrated in Figure 4. Because it is more
automated, overhead charging is becoming morecommon for larger scale deployments and is the mostappropriate mechanism for CTA’s needs, althoughsome plug-in charging may continue to be used ina limited maintenance function. Overhead charging
is already in use for CTA’s current electric buses atseveral on-route and garage locations.

Figure 4 – Photo of pantograph charger at Navy PierAn additional differentiation between charging
technologies involves the speed or power level of thecharging. Charging buses can take place with either
lower-power “slow chargers,” where buses are parked
overnight, or with higher-power “fast chargers,” wherebuses charge relatively quickly at on-route locations
and/or at the garage before they are parked for the
CHARGING FORWARD | CTA BUS ELECTRIFICATION PLANNING REPORT

17night, more similar to current diesel fueling operations.
While fast chargers on the market today have one
dispenser to charge one bus at a time, slow chargers
may have multiple dispensers so that multiple buses
can draw power from one charger.
Overhead charging can be used for both slow charging
and fast charging. For our purposes, we will refer to125-250 kW power as “slow charging,” and 450-750
kW power as “fast charging.” Based on our assumed
battery sizes, a fully depleted battery will take nearly
three hours to charge using slow charging, and a little
less than one hour using fast charging.6 These two
types of charging are suited to different operational
applications, described further in Chapter 2.
Charging operations can also be classified according
to whether they occur at garages or on-route
locations. If the majority of charging can be centralized
at garages, charging is planned as part of evening andovernight bus servicing. Garage charging can utilize
either slow chargers or fast chargers, and different
strategies may be considered based on whether thefacility includes indoor climate-controlled storage oran outdoor storage yard. On-route charging can utilize
the time that a bus spends at layover locations, which
is typically 3-15 minutes. Layover locations are at theend points of routes where additional time is alreadybuilt into the schedule to allow any late-arriving buses
to realign with schedules for their following trip. Onroute charging must use fast chargers, as it seeks totransfer as much power as feasible within a relatively
short time. Even if most charging takes place atgarages, some degree of on-route charging can bevaluable to help extend the range of buses that areoperating longer vehicle blocks.

6 Charge time estimates are based on the capacity of new batteries,
rather than the reduced capacity as batteries degrade over years ofuse. The time required to fully charge would go down with this reduced
capacity, as would the effective range of a fully charged battery, whichis accounted for in analyses.
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Focus: Hydrogen Fuel Cell Electric Buses

Throughout Charging Forward, we use the term “electric bus” to refer to battery electric buses that use
batteries that charge from the electric grid. Hydrogen fuel cells can also be used to produce electricity
for a bus; these vehicles can be referred to as hydrogen fuel cell electric buses. Like battery electricbuses, hydrogen fuel cell electric buses are a technology CTA can consider to eliminate bus tailpipe
emissions. They may be beneficial in some contexts because they have greater operating range andlower weight than battery electric buses.
A hydrogen fuel cell electric bus uses hydrogen and oxygen to produce electricity that powers thebus and emits only water vapor. Most use a hybrid system, in which a battery handles all vehicle
performance needs and the fuel cell continuously charges the battery to extend the range of the vehicle.
The hydrogen fuel for these buses must be stored, compressed, and dispensed using equipment andoperations similar to those used for compressed natural gas fueling.
Hydrogen fuel can be produced in various ways, but for hydrogen that does not rely on fossil fuels
for production, the primary method is electrolysis. Electrolysis uses an electric current to decompose
water into hydrogen and oxygen. Some agencies run electrolysis on-site to produce hydrogen; anotheroption is to have hydrogen delivered by a supplier.
Adoption of hydrogen fuel cell electric buses presents several challenges:• Hydrogen fuel requires substantial safety and fire protection retrofits for CTA’s repair
and refueling facilities. This would be a major challenge for CTA’s older bus facilities.
• Hydrogen fuel is currently more costly than electricity. While the price of hydrogen varies
across the United States, hydrogen currently costs substantially more than electricity for anequivalent amount of usable energy.
• The vehicles are currently more costly than battery electric buses. While both technologies
are currently more expensive than diesel buses, hydrogen fuel cell electric buses are typicallyat least $200,000 more expensive than battery electric buses.
• Greater industry experience with hydrogen fuel cell electric buses is needed before CTA
could make this technology a large part of its plans. Thus far the technology has only beenused for pilot projects in relatively few locations, mostly in California.
Hydrogen fuel cell electric bus technology is a promising technology with particular utility as a range
extender that could be a solution for electrifying some of CTA’s longest vehicle blocks that require agreater mileage range between charges than may be feasible to achieve with battery electric buses
alone. CTA will continue to monitor the development of hydrogen fuel cell electric bus technology,
including through site visits to other agencies conducting pilots, and may pilot it at some point.

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Chapter 2. Initial Fleet Electrification
Analyses
The flow chart in Figure 5 shows the overall study approach. Our firstphase of analyses focused on questions related to when bus purchases
would need to occur, how the rollout might prioritize and sequence
different garages with respect to equity, where charging might occur,and what facility upgrades are needed—these five initial analyses areshown in the left-most column in the flow chart and are summarized inthis chapter. The results of these were then used to develop more specificelectrification scenarios for additional modeling, described in Chapters
3 and 4.

        

  
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  
 

Figure 5 – Flow chart illustrating overall study approach.

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2a. Bus Purchasing Timelines
As noted, CTA currently has over 1,800 buses in its fleet. Each CTA bus is expected tohave a useful life of 14 years,7 and purchases of new buses are planned accordingly,
so a full turnover of the bus fleet typically takes more than a decade. The 14-year
lifetime means that 2026 is the year after which only electric buses can be purchased,in order to meet the 2040 full fleet electrification target date.8 The graph below shows
an example timeline of how the makeup of the CTA bus fleet could change in futureyears to meet the target of 2040 for full fleet electrification. While we do not show
exclusively electric bus purchases beginning until 2026, CTA has already purchased
25 electric buses and plans to purchase more between now and 2026.9
Electric
Non-electric

Potential Timeline for Transition of CTA Bus Fleet
100%

Portion of Bus Fleet

90%
80%
70%
60%
50%
40%
30%
20%

Equivalent toof Electric Buses

2039

2040

2038

2036

2037

2034

Equivalent to
3 Garages worthof Electric Buses

1 Garage worth
2 Garages worth
Potential Timeline of Facility
Upgrades

2035

2032

2033

2030

Equivalent toof Electric Buses

2031

2029

2028

2027

2026

2025

2023

2024

0%

2022

10%

Equivalent to 4, 5, 6, 7, 8 Garages

Planning/Concept
worth of ElectricDesign
Buses
Implementation
Infrastructure
in place
to would
support be needed to
Figure 6 – Graph of potential CTA bus fleet transition timeline. Figures represent
purchasesthat
scaling up electric buses
replace all buses after 14 years.
Chicago
103rd

2040

2039

2038

2037

2036

2035

2034

2033

2032

2031

2030

2029

2028

2027

2026

2025

2023

2024

2022

The graph also shows that the portion of the bus fleet that CTA replaces is not constant
77th
every year,Southbutinstead the purchasing schedule is “lumpy” with more purchases
Shops
concentrated
74th in certain years, and especially towards the end of the transition
Garageperiod. TheNew
purchasingschedule determines the magnitude of facilities with charging
Kedzieequipment needed each year to serve the electric bus fleet. The labels at the bottom ofForest Glen
the graph show
North Parkthat approximately one garage worth of electrified capacity is neededby 2026, two garages worth of electrified capacity are needed by 2029, and so forth.
This is to help give a sense of scale of the charging infrastructure needed at points
along the transition timeline; in practice, multiple garages could have mixed electricand diesel fleets throughout the transition.
7 The Federal Transit Administration’s minimum requirement is utilization for 12 years based on full depreciationof a standard transit bus.
8 To simplify analysis, we assume that no buses are retired before the end of their useful life and that no buses
are kept beyond their useful life.
9 While retrofitting existing buses is possible, and one peer agency is known to be trying this, it is not yet shown
to be cost effective, so our scenarios focus on the conversion through purchase of new electric vehicles toreplace diesel vehicles as they reach the end of their useful life and are retired.
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2b. Equity Analysis
Certain parts of the Chicago region, including many
areas with low-income and minority populations,are disproportionately affected by air pollution andassociated health issues today.10 CTA buses constitutea very small percentage of vehicles on the road andcontribute a relatively small amount to overall local
air pollution.11 Buses also contribute to cleaner air byreducing the overall number of car trips made, andcontribute to equity goals by providing affordable
access to residents of all incomes throughout theCity. Nonetheless, CTA’s current buses are heavyduty vehicles with large diesel engines that generate
air pollution, so one of the primary benefits of
CTA’s deployment of electric buses is that healthimpacting tailpipe emissions from buses would benearly eliminated. CTA has an opportunity to help
address existing inequities by prioritizing bus fleet
electrification in these areas, leading by example forother fleet operators. Electrification of our garages
in these areas could also help push forward the grid
infrastructure upgrades required to support charging,and the improved power infrastructure investment will
benefit nearby residents and employers.
Electrifying CTA’s bus fleet will reduce local healthimpacting emissions from buses by 98% or more.
This includes emissions of NOx, which contribute torespiratory issues including asthma, and emissions offine particulate matter, which contribute to respiratory
issues including chronic obstructive pulmonary
disease (COPD) and cardiovascular issues such asheart attacks and strokes.12
10 Based on a review of the Chicago Air Quality and Health Index (CAQHI) developed by the Chicago Department of Public Health.
More information is available at www.chicago.gov/city/en/depts/cdph/provdrs/healthy_communities/svcs/air-quality-and-health.
html
11 On Ashland Avenue (Routes #9 and #X9) and Western Avenue (Routes #49 and #X49), two of the highest bus frequency corridors
in the city, CTA buses constitute less than 2% of vehicles daily, based on comparison with IDOT’s reported 2018 Average Annual Daily
Traffic data for the segment near Madison Street). CTA’s garages do not stand out as air quality “hot spots” within their communities,
based on a review of Chicago Air Quality and Health Index exposures data. CTA’s emissions of particulate matter have been declining
sharply over the past decades due to improvements in diesel bus technologies.
12 American Lung Association. What Makes Outdoor Air Unhealthy. www.lung.org/clean-air/outdoors/what-makes-air-unhealthy
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The map below illustrates the Chicago Air Quality and Health Index (CAQHI) developedby the Chicago Department of Public Health. This index combines pollution burden
and population vulnerability/sensitivity to better reflect the impacts of pollution oneach community. The higher scores, indicating a greater burden, are concentrated on
Chicago’s South and West Sides. This highlights the importance of planning bus fleet
electrification to prioritize these communities.
To analyze the potential equity-related impacts of electrification, we first considered
two indicators that CTA already utilizes for various evaluations of potential service
and fare changes: presence of minority populations, and presence of low-income
populations.13 Analyses of these populations were developed using two approaches:
one using the population residing near each bus garage within ½ mile, and one using
CTA’s classification of each garage’s bus routes that serve minority and low-income
populations. (See page 8 for a map of where CTA’s bus garages are located, and theroutes that are based at each garage.)

Figure 7 – Map of the CAQHI index throughout Chicago
13 Minority populations must be considered under Title VI of the Civil Rights Act of 1964, and low-income
populations must be considered under Executive Order 12898 on Environmental Justice. We focused on the same
populations as the federal requirements, but this analysis is not intended to fulfill any reporting requirements.
While the federal requirements seek to avoid and mitigate inequitable negative impacts, our analysis went
beyond those requirements and sought to prioritize benefits for historically marginalized communities.
CHARGING FORWARD | CTA BUS ELECTRIFICATION PLANNING REPORT23

A summary of the results of these analyses is shown in Table 1 below. It shows that fiveof CTA’s bus garages serve areas with relatively high proportions of minority and lowincome residents, leading to “high” or “very high” classifications with respect to equitybased prioritization. There are not dramatic differences between these five garages.
Only two garages have significantly different results leading to classifications as “low”
or “medium” priority: North Park Garage and Forest Glen Garage on Chicago’s NorthSide.
Table 1 – Ratings of CTA bus garages based on minority and low-income populations
near each garage and its associated routes.
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The different equity indicators are classified indifferent ways:•

Low income by route and minority population
by route: We define low scores to indicate thedemographic classification applies to < 30% ofroutes, Medium is 30 to 50%, High is > 50%.

•

Low income near garages: We define low scoresindicate the demographic group represents < 20%of the population, Medium is 20 to 35%, High is> 35%.

•

Minority population near garages: We define
low scores to indicate the demographic grouprepresents < 30% of the population, Medium is 30
to 50%, High is > 50%.

•

Overall rating based on average of the four federal
indicators, with Very High > 65%.

Following this, a similar supplemental analysis was completed using the Chicago Air
Quality and Health Index, which, as described previously, combines pollution burdenwith population vulnerability/sensitivity.
Table 2 – Ratings of CTA bus garages based on the CAQHI scores near each garage andits associated routes.
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CAQHI: Low scores are < 35, Medium is 35 to 55, High is > 55.

CHARGING FORWARD | CTA BUS ELECTRIFICATION PLANNING REPORT

24
24

The results of this second analysis largely align with the results of the first; both point
to a prioritization of the first five garages listed in both Table 1 and Table 2, and among
those five all have similarly high priority. These are the CTA bus garages that arelocated in and serve the communities who need the benefits of electric buses most.

2c. Schedule Compatibility Analysis
As noted in Chapter 1, current electric bus battery technology can conservatively
be expected to provide an effective range of approximately 60 miles for a standard
40-foot bus on one full charge. However, many of CTA’s current scheduled vehicle
blocks are much longer—on weekdays, 19% of blocks are between 100 and 150 miles,
and 12% are even longer than 150 miles. Technology is improving, and electric bus
ranges are expected to increase, so it is important to compare CTA’s current service
schedules with both current and improved technology scenarios in order to assess
how much bus service can reasonably be expected to be compatible with electric bus
technologies by 2040.
The compatibility of CTA bus schedules with electric bus technologies was analyzed
through a detailed modeling exercise in order to identify which parts of service may be
more challenging to electrify, especially in the near term, and to help guide the rolloutof electric buses and chargers to optimize compatibility.
This modeling was completed for every scheduled vehicle block14 on weekdays andSaturdays from CTA’s Fall 2018 service.15 It was important to model both weekday
and Saturday schedules because they have significantly different service profiles:
typical service frequencies on weekends are more even across the day, compared to
weekdays which typically have significantly more frequent service during the rushhour peaks. This results in a greater percentage of longer vehicle blocks on weekends.
The service profile on Sundays is similar to Saturday, so the model results for Saturday
can also be used as a proxy for Sunday.
For both day types, the three different technology assumptions defined in Chapter 1
were modeled: current technology, moderate technology improvement, and significant
technology improvement. The modeling also tested two potential networks of on-routecharging locations: one limited network with 13 locations, and one more extensive

14 “Vehicle block” is defined as an assignment of work, for a single (non-specific) vehicle, outlining all trips, bothrevenue and non-revenue, and any recovery time between those trips. A vehicle block typically starts and ends
at a garage, but some have alternate start/end locations.
15 These schedules represent the maximum bus service in that year. While there have been some schedulechanges since then, these changes should not significantly impact the results. We assume that there will be no
impact on public-facing service schedules as a result of electrification.
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25

network with 56 locations.16 The model reflects that the state of charge (SOC) of eachvehicle’s battery declines based on the miles operated and increases when on-routecharging occurs. If the battery SOC fell below a minimum threshold of 20% at any
point, the vehicle block was determined to be incompatible with that technology.
The overall results of this schedule modeling are shown in the table below.
Table 3 – Percent of Fall 2018 vehicle blocks compatible with electrification under different daily schedules, on-routecharger networks, and technology levels  ­  

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The vehicle blocks that are classified as “incompatible” by the model either have
longer mileages to operate, insufficient opportunities to charge on-route, or both. Thismeans that besides adding on-route charging locations, the main strategy to increase
compatibility would be to modify vehicle block schedules by splitting them apart into
shorter mileage assignments to deliver the same service. For example, instead of one
bus making five round-trips on a particular route, it would need to return to the garage
after just three trips, and the last two trips would need to be served by a different
bus. This approach requires some additional bus operator labor hours, increase to thetotal miles driven, and may also require some additional vehicles.17 Other schedulingstrategies were also analyzed, such as allocating additional charging time at layover
locations with on-route charging. These can also be considered in some cases, butwould not be sufficient to make all incompatible blocks compatible.

16 The locations for on-route chargers in these networks were assumed to be existing layover locations and wereselected based on site feasibility and the potential need for on-route charging based on schedules; These should
be considered model networks only; any future on-route charger locations will be selected based on subsequentand more detailed evaluation, and corresponding rollout of garage-based charging.
17 The potential increase in total miles operated is modest, estimated to be at most 6.2%; this increase does notoffset the overall benefits of bus electrification with respect to air quality and climate change.
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Several conclusions can be drawn from the results summarized in Table 3:• Significant percentages of CTA’s bus service are already compatible withelectrification using current technology. This is true even when just limiting
charging locations to garages; more than half of CTA’s weekday bus service iscompatible using current technology, without any on-route charging locations.
• Predictably, schedule compatibility increases with more on-route charging
locations and with more technology improvement. The more extensive onroute charger network makes a significant portion of vehicle blocks compatible
if using current technology, but as technology improves, the need for on-routechargers declines.
• Saturday schedules are less compatible than weekday schedules—as noted,
this is because Saturday schedules have a larger percentage of longer vehicle
blocks. Even with improved technology, Saturday schedules remain moredifficult to electrify.
• Technology improvement alone will not make full electrification of current
schedules possible, but it can bring us to the point where the necessity ofother changes, such as schedule changes or additional on-route locations, isminimized.
While the analysis showed that a more extensive on-route charger network would
increase schedule compatibility, there are reasons to be cautious about planning foran extensive on-route charger network. The analysis also showed that the benefit ofmany on-route locations will decline as technology improves over time, indicating arisk of building excess on-route chargers that become redundant over time. A more
extensive on-route charging network would also increase the overall complexity ofcharger operations, reduce CTA’s flexibility to modify bus route terminal locations
based on future needs, and create new obligations for CTA maintenance personnel totravel extensively throughout the city. It is also important to keep in mind that even avery robust on-route charger network would still require some garage-based charging.
Our analysis showed that if on-route charging was installed at all 78 layover locations
deemed feasible systemwide, but no charging at garages was available, around
66% of weekday vehicle blocks and 55% of Saturday vehicle blocks would remain
incompatible, even with significantly improved technology.18 Finally, a preliminary
comparison of up-front infrastructure costs and potential long-term operating savings
found that there would not likely be any cost advantage to building the more extensive
on-route charger network.

18 All current layover locations were evaluated. A location was deemed feasible if it was off-street with sufficientspace for at least one charger and associated power cabinets, while still allowing for a passing lane in the case of
more than one bus accumulation.
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Based on the results of these analyses, CTA recommends the following strategies:• Prioritize charging at garages and develop a limited network of on-routechargers. Centralized charging at garages yields simpler operations, and asignificant portion of CTA’s bus service can be electrified using garage charging
alone. Adding a limited network of on-route chargers, similar in magnitude to
the set of 13 on-route charging locations that was modeled, would enhanceschedule compatibility without adding excessive cost and complexity.
• Adapt based on experience and advances in technology. As technology
continues to develop and CTA gains more experience with its performance,
CTA will be able to refine recommendations for the locations of the limited onroute charging network in order to achieve full electrification most efficiently
and cost effectively. As more is known about future technology performanceand we approach the need to electrify the least compatible vehicle blocks,
the additional cost and complexity of adding more on-route locations can beweighed against other means of increasing compatibility, such as modifying
vehicle schedules.

Focus: Red Line Extension Coordination
When the Red Line Extension (RLE) is
implemented,
somecomplementary
bus network restructuring will occur
to integrate and connect the new rail
stations. We used the preliminary plan for
the restructured bus network to evaluate
impacts on schedule compatibility andthe need for on-route charging. While itis not clear that on-route charging will beneeded at the new station locations, theplans for RLE stations with adjacent offstreet bus facilities are being developed
to be forward compatible with potential
electric bus charging, to the extent costefficient and feasible.
Figure 8 – Map of proposed new Red Line Extension. New stations proposed at Michigan Avenue and 130th Street
are anticipated to have off-street facilities for bus connections that could potentially also serve as on-route electriccharging locations.

CHARGING FORWARD | CTA BUS ELECTRIFICATION PLANNING REPORT28

2d. Garage Charging Strategies
As described in Chapter 1, electric buses utilize twomain types of chargers:• Slow chargers add energy to a vehicle’s battery
at a more gradual rate, and are typically used at
the location where the bus is parked overnight,
with each bus connected to a charger. Twoor three buses can share one slow charger
with multiple plug-in or overhead pantographdispensers, but essentially each bus has its
own charging “spot” for the night.
• In contrast, fast chargers come closer tomimicking current diesel fueling operations—abus pulls up to a charger, recharges for a
relatively short time as energy is transferredmore quickly, and is then parked elsewhere to
be stored overnight so that other buses canuse the fast charger.
The time required for a bus to fully charge depends
on how depleted the bus’s battery is when it begins
charging, just like the time it takes to fill an empty fueltank depends on whether it is partially or completely
empty. Today, when a CTA bus returns to its garage
after completing its daily trips, it typically spends 15
minutes in a fueling lane, during which time refuelingand basic interior cleaning takes place. For electricbuses returning to the garage with only a modestly
depleted battery, charging at a fast charger could takeplace within a similar window of time, and simultaneouswith routine servicing activities. For electric buses
returning to the garage with a more significantly
depleted battery, 15 minutes on a fast charger would
not be enough to fully recharge.

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29

However, charging a fleet does not have to be done
all one way or the other. Different combinations of fastand slow charging are possible, and each method
DRAFT For Internal Discussion Purposes Only
has
different advantages and disadvantages. These
differences include the number of chargers needed, thecost per charger, the physical space impacts, the peak
power draw required, the degree and type of changes
to servicing operations needed, and the degree towhich the technology has been tested under different
conditions. So CTA faces a strategic choice: what mix
of fast and slow charging will be most efficient, reliable,
and cost effective overall?
Our analysis tested a full spectrum of approaches withthe goal of ensuring that each bus is fully charged
before it pulls out for its first trip of the day. The results
indicate key differences with respect to infrastructure
costs, the space needed for chargers, the labor needed
to 1
Equivalent to 2
Equivalent to 3
for operations, and theEquivalent
peakelectrical
power
draw
Garage worth
Garages worth
Garages worth ofof Electric Busesof Electric BusesElectric Buses
needed.

“CTA faces a strategic
choice: what mix offast and slow charging
will be most efficient,reliable, and costeffective overall?”Equivalent to 4, 5, 6, 7, 8
Garages worth of Electric Buses

Slow charging inparking space

Bus returning
to the garage

Fast charging duringservicing in fuelinglanesPark in space
without charger

If needed, additional
fast charging
Figure 9 – Conceptual illustration of potential garage charging operations that were evaluated

The graphic in Figure 10 summarizes the range of garage charging strategies that wereconsidered. At one extreme, charging could be achieved with “All Slow Charging,”
defined as slow chargers available for all buses at a garage, in the locations where thebuses are parked overnight. This has been a common strategy for many of the initialsmall-scale electric bus deployments. In practice, at least one fast charger would
probably also be installed at each garage for maintenance and resiliency purposes.192

19 Note that this charger is not assumed to be used as part of daily scheduled operations, and the analysis ofcharging and costs reflects this.
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30

For larger scale implementation, it may make sense to install fast chargers at thelocations of the current fueling lanes, so that buses have the ability to charge whileother servicing activities take place, which would be sufficient for buses that areassigned to shorter vehicle blocks and return to the garage with a relatively high SOC.
We therefore defined the second strategy as “Moderate Fast Charging,” with one fast
charger per current fueling lane at each garage and the assumption that each bus
could spend 15 minutes at the fast charger during daily bus servicing. In this case, allbuses that could not be sufficiently charged in that time would be stored overnightconnected to a slow charger.
The third strategy, “Mostly Fast Charging,” tested a greater amount of fast charging,with two more fast chargers installed at each garage in addition to the one fast charger
per fueling lane included in the previous strategy. These additional fast chargers
would likely be installed at other locations within each garage, and their use would
be prioritized for buses that require a brief “top-off,” to reach their target SOC. Thisapproach maximizes usage of the fast chargers and helps reduce the need for slow
charger infrastructure. As in the “Moderate Fast Charging” strategy, a sufficient numberof slow chargers is included to serve any buses that could not be fully charged using
fast chargers in the time available, but the number of slow chargers needed would
DRAFT For
Purposes
Only
declineasInternal
moreDiscussion
buses cancompletecharging on fast chargers.

Fast Charging

Slow Charging

All Slow Charging

Moderate Fast Charging

All Fast Charging
Not analyzed in detail

Mostly Fast Charging

Figure 10 – Different combinations of slow charging and fast charging are possible at garages.

Standard Bus Equivalents

1 – Different
combinationsof slowof
charging
and fastcharging”
charging are possible
garages.
InFigure
theorya fourth
strategy“all fast
couldat beconsidered as well, but thiswas not analyzed in detail because it would necessitate including some fast chargers
Bus Assignments and Capacity by Garage
that would not be well utilized—theywould
be needed only to serve a relatively small
Design Capacity
Buses Assigned
number of400buses every day and therefore be less cost efficient.
In addition, having
350
350
310.5
some mix 300
of fast 282.5
and slow technologies
is desirable for the foreseeable future as both
274
273
262
260
250 will evolve and may perform differently, particularly with respect totechnologies
200
battery degradationand extreme temperatures.
150
100
50
0

103rd

74th

77th

Chicago Forest
KedzieGlen
Bus Garages
Figure 2 – Graph comparing bus assignments and design capacity at garages
Source: Summer 2019 Fleet Summary
CHARGING FORWARD | CTA BUS ELECTRIFICATION PLANNING REPORT

North
Park

31

These different potential garage charging strategies were analyzed using the resultsof schedule modeling described in Section 2c, using the limited network of on-routecharger locations and assuming that technology aligns with “Moderate Technology
Improvement.”20 For vehicle blocks that were found to be compatible with electrification
under those assumptions, the amount of charging energy needed was calculated as
the difference between the end-of-service SOC and the target SOC expected forbuses beginning service. In cases where buses would be stored outdoors and notconnected to a charger, the target SOC was set higher, to account for extra energy
needed for battery heating during winter conditions.21 The use of chargers was also
scaled up to reflect full fleet electrification, including all vehicle blocks. The analysis
was used to estimate the following for each of the three garage charging strategies:• The number of fast chargers and slow chargers needed, and associated costsof charging equipment. One fast charger costs more than one slow charger,
but fast chargers can be shared by more buses every day, and so can be lessexpensive on a “per bus” basis depending on overall usage.
• The garage’s electrical capacity needed, based on peak power draw. Fast
chargers use higher power levels, but fewer are generally needed; this results
in a lower combined peak power draw. Section C of the Appendix describes
the analysis of peak power draw expected based on garage charging
strategies; this informs the electrical capacity upgrades needed from ComEd
and associated costs.
• Impacts on bus storage space from slow charging equipment, due to the rowsof electrical cabinets and overhead gantry footings needed. These impacts
were assumed to be smaller at indoor garages, where gantry footings can bealigned with existing columns.22• Additional servicer labor required for any buses that are assumed to needadditional fast charging beyond the time they currently spend in fueling lanes,
and associated labor cost.

20 The limited network used is the example network of 13 on-route charging locations as discussed in Section 2c.
In practice the precise number and locations of on-route chargers may vary based on further analysis.
21 This would apply to fast-charged buses at CTA’s two outdoor garages, Forest Glen and North Park.
22 Slow chargers may also reduce operational flexibility, making their impacts larger. Fast charging equipment
also takes up space, but we make the assumption that the necessary number of fast chargers can fit within the
garage space currently occupied by fueling islands or other space available at the garage.
CHARGING FORWARD | CTA BUS ELECTRIFICATION PLANNING REPORT

32

The table below summarizes results from this analysis for one garage, 74th Street
Garage, as an example. It shows that strategies with more slow chargers have relatively
high costs for the chargers themselves; as noted, this is because the costs of fast
chargers can be more effectively “spread” over many buses. Using more fast chargers
also reduces the total peak power needed because, although they draw more power
individually than slow chargers, fewer are needed. Having more slow chargers also
requires more space, and while the space needed just for equipment itself is estimatedto be modest, the fact that CTA’s bus garages are already over capacity means thatany spatial impacts could be difficult to manage. Finally, the results show that bus
servicer labor increases with more fast charging, though the overall costs of the labor
are generally modest as well.
Table 4 - Example analysis results from 74th Street Garage.
* “Added Bus Servicer Labor” refers to the staff time that would be needed to conduct fast charging outside of the current
standard 15-minute servicing time period.
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Overall, the results suggest that there are a number of advantages to using a significant
amount of fast charging at garages. However, there are also concerns about fast
charging that may justify caution. Repeated fast charging may cause greater battery
degradation over time, and there is relatively little peer agency experience with storing
fast-charged buses outdoors in cold climates while not connected to a charger, so it
is still unknown how well the bus batteries would perform in these conditions. Basedon these considerations, all three garage charging strategies (“All Slow Charging,”“Moderate Fast Charging,” and “Mostly Fast Charging”) were recommended for further
evaluation in the next stage of analysis (Chapter 4).

CHARGING FORWARD | CTA BUS ELECTRIFICATION PLANNING REPORT

33

2e. Facility Upgrade Needs
CTA’s bus facilities include seven garages, shown on the map on page 8, and one
heavy maintenance facility, South Shops, that is co-located with the 77th Street
Garage. Charging infrastructure and additional power supply will need to be added toall of these facilities in order to achieve electrification of the full fleet. In addition, due
to a chronic lack of sufficient available funding, many of these facilities have significant
deferred capital maintenance and modernization needs, some of which will need tobe completed to ensure a successful implementation of the conversion to electricbuses. Adding new technology that is heavily dependent on integration with existing
structural, electrical, and mechanical systems means that facility upgrades that havebeen deprioritized due to limited funding can no longer be delayed.
It is also important to note that most of CTA’s bus garages currently serve and store
more buses than they were designed for, which causes operational issues already,and means there is very little flexibility to accommodate installation of new equipment
or adjustments to patterns of bus operations and storage. Planning for bus fleet
electrification must address these conditions, even though the required upgrades
may not be directly tied to electrification.

Facility Assessments
In order to account for the overall facility needs, information was compiled on the
upgrades needed for each facility. Associated order-of-magnitude costs were also
estimated and compiled to be used in the scenario modeling described in Chapter
4. The following discussion is intended as a high-level overview to identify the typesof investments that should be expected; more detailed analysis will be needed todetermine all facility-specific improvements and refined costs.
First it should be noted that Forest Glen and North Park are the only two CTA bus
garages that currently have all outdoor storage for buses; this feature has implications
for electric buses that are discussed in more detail below. Separate from electrificationneeds, the extent of upgrades needed varies considerably among facilities. Threeof CTA’s bus garages need significant modernization, which includes replacementof buildings, equipment, and paved areas: 77th Street, Forest Glen, and North Park
Garages. The 77th Street Garage is part of a large site that also includes the South
Shops heavy maintenance facility; this complex of facilities should be studied as a wholeto plan for comprehensive modernization needs. Significant upgrades are needed at
74th Street Garage, including roof replacement, and at 103rd Street Garage, including
roof and pavement replacement. Kedzie Avenue and Chicago Avenue Garages havemore moderate upgrade needs, such as pavement work and boiler replacement.
CHARGING FORWARD | CTA BUS ELECTRIFICATION PLANNING REPORT

34

Different types of upgrades were classified into two categories, as shown in Table 5
below. Some upgrades, such as charger systems, will be needed specifically for electricbuses. Other upgrades also may be essential to complete as part of conversion toelectric buses, depending on the conditions of each facility. New equipment may havephysical impacts that trigger additional building or fire/life safety code requirements,
prompting additional work. Conditions discovered in the course of implementation may
necessitate additional repairs. Other facility upgrades may be advisable in order to help
protect the investment in charging infrastructure or efficiently stage work and avoid
duplicating effort. For example, if gantries for slow chargers are installed throughout agarage’s bus storage area, that installation should be planned to occur simultaneouslywith any needed replacement of pavement and other adjacent infrastructure. Other
state of good repair upgrades may be ideally planned to coincide with the upgrades
to accommodate electric buses, but would not necessarily be required to achieve
electrification. Further study of each facility will be needed to determine which repairs
and upgrades must be done to enable electrification, and how best to strategicallyprogram them given available funding.
Most of the facility needs listed in Table 5 are the same regardless of charging
strategy, although centralizing more charging at garages (versus on-route) predictably
increases the need for charging infrastructure at garages, and converting outdoor
storage to indoor facilities may be more important for strategies that rely more heavily
on fast charging, as discussed more below. Strategies that rely more heavily on slow
charging will also likely have a somewhat larger impact on facilities because thephysical footprint of the installations would be larger, and so may lead to a greaterneed for timing other facility upgrades to be simultaneous.
Table 5 – Classification of facility upgrades
Note that these lists are not meant to be exhaustive.
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CHARGING FORWARD | CTA BUS ELECTRIFICATION PLANNING REPORT 

35

DRAFT For Internal Discussion Purposes OnlyBus Storage Capacity Needs
As noted earlier, most of CTA’s bus garages are currently storing buses in excess of
their design capacity. This means that the placement and flow of buses may alreadybe suboptimal, causing operational inefficiencies. It also means that there may belittle or no room for additional equipment. Figure 11 below illustrates how the numberof buses assigned compares to capacity at each garage.23 Systemwide, CTA has abus storage space deficit of over 200 standard bus equivalents (SBE).24 This situation
would likely be exacerbated by electric bus implementation; installation of charging
infrastructure
is Charging
expected to require
All Slow
Charging and associatedModeratenew
Fastoperational
Charging requirements
All Fast Charging
Mostly Fast
Not
analyzed in detailmore space, not less. As a result, the existing shortage of bus storage capacity willneed to be addressed as part of the fleet electrification process.

Fast Charging

Slow Charging

Figure 1 – Different combinations of slow charging and fast charging are possible at garages.

Bus Assignments and Capacity by Garage
Standard Bus Equivalents

Design Capacity
400
350
300
250
200
150
100
50
0

282.5

103rd

Buses Assigned
310.5

260

273

274

262

74th

77th

ChicagoForestGlen

KedzieBus Garages
Figure 2 – Graph comparing bus assignments and design capacity at garages
Figure 11 – Graph comparing bus assignments and design capacity at garages
Source: Summer 2019 Fleet Summary

350

North
Park

Source: Summer 2019 Fleet Summary

23 Note that this figure represents Summer 2019 conditions. Since then, some buses have been shifted among
garages, but overall fleet size and capacity issues remain the same.
24 Bus storage capacity is measured in standard bus equivalents (SBE), in which a standard 40-foot bus iscounted as 1 SBE and an articulated 60-foot bus is counted as 1.5 SBE.
CHARGING FORWARD | CTA BUS ELECTRIFICATION PLANNING REPORT

36

CTA has identified three potential projects that could help address bus storage
capacity:• Identify a site and construct a new additional bus garage. While a specificlocation for a new garage has not been selected, the scale of the current storage
capacity deficit indicates that a new garage is needed, even before accounting
for the increase in storage space needs that may result from electrification.
A new garage may also prove critical for temporary use by displaced buses
during the construction involved with major upgrades at other garages. For
analysis purposes we assume that a new garage could house 250 SBE, which
is similar in size to most of CTA’s existing garages.
• Reconfigure Forest Glen Garage utilizing CTA-owned parcels. CTA owns
property adjacent to the existing footprint of the garage facilities; reconfiguring
and improving these parcels for garage use could add an estimated 101 SBEof storage. There is an existing need to reconfigure this facility for operational
reasons regardless of capacity needs.
• Reconfigure North Park Garage utilizing CTA-owned parcels. CTA owns
property at North Park that is now used for employee parking. Reconfigurationand improvements to the site could add an estimated 40 SBE of storage.
Electrification scenarios that include a new garage, and variations with respect toreconfigurations at Forest Glen and North Park, were recommended for further
evaluation in the next stage of analysis (Chapter 4).

Considerations of Outdoor Storage
Finally, it should be noted that while most of CTA’s bus garages store buses indoors
with climate control, two of CTA’s bus garages, Forest Glen and North Park, currently
utilize outdoor bus storage. Outdoor storage can be cost efficient and provide more
flexible movement of buses compared to indoor, but it also means buses are subject tothe elements and extreme temperatures. Cold temperatures, in particular, have specificimplications for electric bus technology, since energy stored in the battery is consumed
by electric heaters to keep the battery at an optimal temperature. Therefore, if buses
are stored outdoors and not connected to a charger, which would be the standard
operation for fast-charged buses, they will need to be charged to a higher SOC before
being parked for the night, to accommodate the additional energy needed for battery
heating. (Our garage charging analysis, in Section C of the Appendix, factors in thisadditional energy requirement.)

CHARGING FORWARD | CTA BUS ELECTRIFICATION PLANNING REPORT37

It should also be noted that during cold weather, CTA’s electric buses currently use
onboard diesel heaters to heat and maintain interior cabin temperature, and will likely
continue to do so for the foreseeable future, although alternative heating technologies
are in development.25 This need will be higher for buses stored outdoors than for buses
stored indoors because their starting temperatures will be lower. Diesel buses stored
outdoors currently get pre-heated on cold days, so this is not a major difference fromcurrent operations. Preliminary analysis showed that the additional costs incurred forbattery and cabin heating for buses stored outdoors are far lower than the costs ofbuilding and maintaining a new indoor garage. However, adding indoor storage lowers
overall risks from weather effects and has other benefits for staff and operations.
Because there are advantages and disadvantages of indoor and outdoor storage withrespect to costs and operations, and because the comparison shifts with different
mixes of fast and slow charging technology, variations with respect to converting
outdoor garages to indoor facilities were recommended for further evaluation in thenext stage of analysis (Chapter 4).

Detailed Facility Planning
Conversion of CTA’s bus facilities to support electric buses will require additional
detailed analysis, planning, and design. Base engineering analysis to model power
demand and prepare specifications will be needed to advance future work. Facilities
studies will include planning, siting, and environmental analysis for a new garage, andplanning for modernization and reconfiguration of 77th Street/South Shops, Forest
Glen, and North Park. An important part of studies for existing facilities will be toidentify which state of good repair needs must, should, or may not need to coincidewith electrification. This work will be coordinated with, and build off of, existingassessments done as part of CTA’s Transit Asset Management planning.
Facility planning will need to address strategies for maintaining operations during thetransition to electrification, such as fueling, charging, bus flows and staffing needs.
It will also be essential to evaluate back-up power solutions, such as onsite power
generation and microgrids, to ensure the reliability of garage charging. Continued
study will also be needed to refine the locations and sequencing of the proposed
limited network of on-route charging locations, and develop detailed designs tointegrate the charging equipment at these sites.

25 The use of diesel technology to heat buses means that diesel fuel consumption and associated emissions
will not be completely eliminated through electrification in the immediate future. Depending on the charging
strategy, annual diesel fuel usage by electric buses is estimated to be 0.2% to 2.2% of the volume that is currently
used to power CTA buses. Alternative heating technologies that do not dramatically reduce battery range are indevelopment but are not widely available at this time.
CHARGING FORWARD | CTA BUS ELECTRIFICATION PLANNING REPORT

38

Chapter 3. Defining Detailed
Electrification Scenarios
Based on the results of the analyses described in Chapter 2, we reachedseveral key conclusions that informed the next phase of analysis:• Prioritizing equity considerations means that bus facilities and routes on
the South and West Sides of Chicago should be electrified first. This meanselectrification upgrades should begin first in the five bus garages in theseparts of the city.
• Charging operations should be centralized at bus garages to the extent
feasible. This should be supplemented with a limited network of on-routecharging locations.
• Three different garage charging strategies should be evaluated, defined as All
Slow Charging, Moderate Fast Charging, and Mostly Fast Charging.
• CTA’s bus facilities have significant state of good repair needs, many of which
may need to be coordinated with the conversion to electric buses, especiallywith respect to the installation of power and charging infrastructure.
• CTA needs a new bus garage to address its existing bus storage capacity
deficit and enable electrification. Reconfigurations of Forest Glen Garage andNorth Park Garage to add more capacity should also be considered.
• While not a prerequisite for conversion to electrification, it may be advantageous
to convert CTA’s two outdoor bus garages, which are Forest Glen Garage andNorth Park Garage, to indoor storage.
These findings were used to develop eight bus fleet electrification scenarios,
summarized in Table 6. The eight scenarios formed the basis for testing different
potential approaches to electrifying CTA’s entire bus fleet by 2040 with respect tothe operating costs, capital costs, emissions, and garage capacity impacts.26 For
scenarios that include Moderate or Mostly Fast Charging, the variable of whether or
not to convert outdoor storage facilities to indoor was also tested, because indoor
storage is expected to be particularly advantageous for buses that are fast-charged.

26 All eight scenarios assume the same level of supplementary on-route charging, using the more limited
model charger network. They also assume Moderate Technology Improvement and use of vehicle schedule
modifications to reach 100% schedule compatibility, which is estimated to generate an increase in operational
labor cost and necessitate a slight increase to the bus fleet size.
CHARGING FORWARD | CTA BUS ELECTRIFICATION PLANNING REPORT

39

All eight scenarios assume a new garage to help address existing capacity issues, andall eight scenarios assume that upgrades to existing garages address all state of good
repair needs.27 Variations with respect to whether additional garage reconfigurations
take place are also included, but it is important to note that this choice is not directly
related to electrification; rather, it is tied to the anticipated level of overall fleet growthover the full transition period, which is uncertain at this point and will be determinedby factors other than electrification. (See page 45 for additional discussion.)
Table 6 - Summary of eight fleet conversion scenarios.
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Timelines and Sequence of Garage Upgrades
The scenario modeling requires defining specific timelines for when bus purchases
would occur and when facility improvements would occur. Since the end date forcomplete conversion is 2040 for all scenarios, these timelines are generally similar,
with minor differences to align electric bus purchases to the facilities’ available
charging and storage capacity. The planned facility improvements are timed to spaceout significant modernization projects; five years apart if possible. They are also timed
to ensure that sufficient charging capacity is always installed and ready to serve thenumber of electric buses planned for each transition year, as the electric portion of the
fleet grows and diesel buses are retired. It is important to note that some garages may
not be fully converted for electric buses all at once; but rather be completed in phases.

27 As discussed in Chapter 2e, it may not be essential to meet all state of good repair needs for bus facilities
before proceeding with electrification, however it is not possible to determine the division of essential and nonessential upgrades without the additional, more detailed, facility planning studies that have been noted as a
critical next step.
CHARGING FORWARD | CTA BUS ELECTRIFICATION PLANNING REPORT

40

All scenarios include upgrading CTA’s bus garages in the same sequence, which was
determined based on the considerations as follows:• First, this sequence prioritized equity considerations. The four garages rated
as “very high” priority for equity were the first four garages to begin receiving
electric buses and charging infrastructure: Chicago Avenue, 103rd Street, 77th
Street, and 74th Street.
• Next, the sequence was adjusted to ensure that the major construction projects
were paced in a way that is more feasible considering the funding, lead time,other resources, and operational disruption involved. This minimizes overlap
between the projects at 77th Street, Forest Glen, and North Park, and the
project of constructing a new garage. We also assumed that each of thesemajor projects would take several years of planning and design and therefore
the earliest possible placement of a major project was third in sequence (77thStreet Garage). The other major construction projects were then timed tominimize overlap.
Table 7 below summarizes these factors and the recommended sequence of garage
upgrades. Note that the place within the sequence refers to the timing of the start datefor implementation of a first phase of electric buses at the corresponding garage, notthe completion date of full conversion of that garage.

Table 7 – Recommended sequencing of bus garages with the factors that were considered

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CHARGING FORWARD | CTA BUS ELECTRIFICATION PLANNING REPORT


41

Electric
Non-electric

Potential Timeline for Transition of CTA Bus Fleet
100%

Potential Timeline of Facility Upgrades

2040

2039

2038

2037

2036

2035

2034

2033

2032

2031

2030

2029

2028

2027

2026

2025

2024

2023

0%

2022

Portion of Bus Fleet

90%
Figure 12 showsa potential timeline for phasing facility upgrades that would introduce
80%electric buses
at each garage following the sequence above. Garages in better
70%
condition may
60% be able to support electric buses relatively quickly through incremental
50%
upgrades tomeet charging requirements; this gives CTA more flexibility in the timing
40%of these garages.
However, the garages that need major construction work, including
30%
77th Street,20%
Forest Glen, North Park, and the new garage, may not be able to begin
10%
serving electric buses until the projects are complete or mostly complete.

Planning/Concept Design
Implementation
Infrastructure in place to supportscaling up electric buses

Chicago
103rd
77th
South Shops
74th
New Garage
KedzieForest Glen

2040

2039

2038

2037

2036

2035

2034

2033

2032

2031

2030

2029

2028

2027

2026

2025

2024

2023

2022

North Park

Figure 12 – Potential Timeline of Garage Upgrades. Note that full garage modernization projects are shown as a five-year
process that includes planning and design.

CHARGING FORWARD | CTA BUS ELECTRIFICATION PLANNING REPORT

42

Accommodating Fleet Growth
Each of the scenarios is able to accommodate a different
level of bus fleet growth, which is a key difference
between them. The level of fleet growth that will beneeded over the next eighteen years is not fully knownat this point (see page 45 for additional discussion), so
different scenarios were developed to be able to fit arange of possible needs. Under each scenario, several
factors can add or require bus storage capacity, andthe resulting balance determines how much fleet
growth can be accommodated. These factors include:
1. In all scenarios, it is assumed that space for
32 additional SBE is needed, to accommodate
splitting apart long blocks to ensure all service
is compatible with electrification.
2. Scenarios using more slow charging areassumed to need somewhat more space forcharging equipment, six or seven square feetper slow-charged bus.
3. In all scenarios, it is assumed that a new garage
is constructed, adding 250 SBE.
4. Scenarios that include reconfiguration of
North Park and Forest Glen assume thesechanges add more capacity; 40 and 101 SBE
respectively. In the scenarios where outdoor
storage at these two facilities is converted toindoor storage, the net addition of capacity islowered to 20 and 81 SBE because of the spaceneeded for new buildings.

CHARGING FORWARD | CTA BUS ELECTRIFICATION PLANNING REPORT43

Table 8 - Summary of eight fleet conversion scenarios including the fleet growth that can be accommodated.
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Notes: The fleet growth figures are the number of SBE that can be accommodated in addition to the 32 added buses
required to split apart long blocks, in order to represent buses that can be utilized for service expansion. A new garage
with “Moderate Fast Charging” is assumed to have four fast chargers and with “Mostly Fast Charging” is assumed tohave six fast chargers, plus any slow chargers needed to charge the balance.

Table 8 shows the overall potential for accommodating bus fleet growth for eachscenario. Three scenarios require keeping the fleet size approximately constant,28
two scenarios allow approximately 100 SBE of fleet growth, and three scenarios allow
approximately 140 SBE of fleet growth.29
These eight model scenarios were selected to allow us to identify the range of impacts
of different potential strategies, and the relative magnitude of tradeoffs among them.
The goal was not to identify one specific “best” scenario that would then constitute
CTA’s final electrification plan, but rather to better understand the effects of varying
possible approaches, in order to inform the key strategic decisions that need to bemade at the outset of electrification. Actual implementation may involve a hybrid ofcomponents from several of these scenarios, and may be refined based on real world
experience as discussed more in Chapter 6, Next Steps.

28 Two of the scenarios show a slight decrease in fleet size, but in practice this can likely be accommodated byslightly adjusting the capacity of the new garage.
29 Because CTA’s garages currently store more buses than they were designed for, a similar evaluation of a“current conditions” scenario without a new garage or any reconfigurations would project a deficit of 238 SBE
compared to the 2021 level.
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44

Focus: CTA Bus Fleet Size in the
Broader Contexts of Climate Change,
Equity, and COVID-19
Nationwide and internationally, the last several years
have brought new public attention and urgency to theissues of climate change and inequity with respect torace and socioeconomics. Simultaneously, the world
has endured and adapted to the onset of the COVID-19
pandemic. All three of these factors have shaped, andwill likely continue to shape, individual attitudes andbehaviors, politics, and public policy with respect topublic transit. This report does not seek to explore
all possible ramifications of these forces, but several
possible impacts are worth highlighting:• A greater focus on slowing and reversing
climate change may increase support for
public transit, both in terms of funding levels,
supportive policies, and individual attitudes
and behavior. It is anticipated that this willlead to increases in public funding specificallyfor electrification of vehicles of all types,
which can reduce climate emissions from thetransportation sector significantly, dependingon the power sources of the grid that vehicles
draw from. Just as important, policies focusedon public transit as a key solution to reducing
the climate footprint of transportation would
seek to shift more trips from low-occupancy
vehicles, such as personal cars, to public
transit; this would point towards the need for
CTA to increase overall service levels and bus
fleet size.

CHARGING FORWARD | CTA BUS ELECTRIFICATION PLANNING REPORT45

• Other sections of this report discuss CTA’s intent to prioritize equity within the planned
sequence of electrification of bus garages and bus routes, in order to reduce health-impacting
air pollution in the communities that most need cleaner air. It is also important to note thatpublic transit, and bus service in particular because of its broader geographic coverage, isa critical transportation option for historically marginalized communities. This means that
increases to bus service can be a key tool for expanding economic access and improving
quality of life for residents and businesses in these areas, and also implies a need for CTA toincrease overall service levels and bus fleet size.
• The COVID-19 pandemic also has potential implications for bus fleet size and electrification.
The pandemic has directly impacted use of public transit, and its lasting effects may continue
to do so, in particular with respect to a predicted rise in telecommuting. As in other cities,
transit ridership in Chicago fell sharply at the start of the pandemic, although CTA’s bus
system experienced smaller losses than its rail system. CTA continued to provide hundredsof thousands of bus rides daily, even when stay-at-home-orders were in effect, including
commutes for essential workers. Since the Spring of 2020, transit use has risen and fallen atvarious stages as the city has moved through different phases of reopening and experienceddifferent levels of prevalence of the disease. Since vaccines became widely available, transit
ridership has gradually been returning, but it is still unclear what the “new normal” will look
like. One possibility is that ridership will largely return, but the traditional AM and PM peaktravel hours will be less busy, with ridership spread more evenly throughout the day. If thishappens, CTA could modify service in order to reallocate some service from the peak periods
to the rest of the day. This type of change would generally lead to longer vehicle blocks that
tend to be less compatible with electric bus ranges, but it may also reduce the need to growthe bus fleet with respect to the number of buses needed during peak hours.

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46

Chapter 4. Cost and Emissions
Projections of Electrification Scenarios
The final phase of analysis completed for this study was detailed modelingof the eight fleet electrification scenarios presented in Chapter 3, inorder to better understand the financial implications of each scenario,
and predict emissions of three key air pollutants. This modeling wascompleted for the entire CTA bus fleet over the period 2022-2040. Table 9
lists the major cost categories and specific types of emissions included inthis modeling. More details of the analysis inputs can be found in Section
D of the Appendix.
As a baseline for comparison, we also included two diesel fleet scenarios in thismodeling. One of these scenarios (D1) represented a no-growth scenario for the fleet
while the other scenario (D2) represented a high-growth scenario. Both of thesescenarios included the facility state of good repair upgrades and capacity increases
that are generally needed regardless of electrification. Scenario D1 included a new
garage to address the existing storage capacity deficit, while Scenario D2 included
reconfiguration of Forest Glen Garage and North Park Garage in addition to a new
garage to accommodate additional fleet growth.
Table 9 – Major cost categories included in cost modeling

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* Only applies to electric fleet scenarios.

30 This includes capital costs for upgrades on CTA’s side of the meter and CTA’s portion of costs on ComEd’s
side of the meter, though some of these costs may be covered by ComEd in the future.

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47

Cost Modeling
In addition to better quantifying the tradeoffs among electrification scenarios, the costmodeling produced an estimated range of the total investment that will be required toachieve full electrification of the bus fleet.
When interpreting the results of this modeling, it should be noted that since CTA
will need to continue operating some diesel buses throughout the transition period,
diesel-related costs decline over time but remain a significant part of overall costs
until 2040 when the last of CTA’s diesel buses are retired. It is also important to notethat the transition-period capital cost projections for electric fleet scenarios are likely
higher than the end-state annual capital costs expected from electric fleet scenarios,
as the transition period will involve significant facility upgrade costs that are needed
to enable the transition. After the transition is complete, ongoing capital investment
to update facilities and replace buses and chargers will still be needed, but would be
expected to drop off significantly. Unless otherwise noted, the results will be presented
in year of expenditure (YOE) dollars, which include future inflation.

CHARGING FORWARD | CTA BUS ELECTRIFICATION PLANNING REPORT48

Table 10 summarizes the estimated total operating and capital costs of the electricand diesel scenarios over the period 2022-2040. It shows that electrification scenarios
have lower operating costs compared with diesel scenarios, but they also require
greater capital investments during the transition. When operating and capital costs
are combined over the 2022-2040 time period, the electric scenarios are projected tobe more costly than comparable diesel scenarios by $1.7 to $2.9 billion.31
Table 10 – Summary of cost modeling results for the period 2022-2040. All cost figures are in billions of YOE dollars. We
define “comparable” scenarios as those that accommodate approximately the same amount of fleet growth.
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                         

31 We define “comparable” scenarios as those that accommodate approximately the same amount of fleet
growth, as specified in Table 10.
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49

Figure 13 presents estimated annual operating and capital costs for each year of thetransition period, comparing the average results from both diesel scenarios and theaverage results from all electric scenarios.32 It shows that operating costs are relatively
stable each year for both, but diesel operating costs grow over time, and by 2040,
the average results from electric scenarios show an operational savings comparedwith the average results from diesel scenarios. Capital costs vary more from year
to year, and they are greater under the electric scenarios compared with the diesel
scenarios, particularly in the second half of the transition period. As noted, for theelectric scenarios, capital costs are projected to be lower on an ongoing basis after
the transition than during the transition period because the initial facility investments
would be complete.

Figure 13 – Projected annual costs comparing average results for electric scenarios (left) and average results for diesel
scenarios (right)

32 These annual cost figures represent the average results of the two diesel scenarios and average results of theeight electric scenarios.
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50

Figure 14 summarizes the estimated 2022-2040 capital costs broken out into major
categories. In total, converting the fleet to electric buses would require an increasein capital funding over the transition period of $1.8 to $3.1 billion on top of the basecost to maintain the existing bus fleet and facilities. The electrification scenarios havegreater costs related to vehicle purchases, vehicle overhauls, electrical upgrades,
and charger infrastructure. The costs related to facility upgrades that relate to stateof good repair, modernization, and a new garage do not drive the increased cost ofelectrification because they are also necessary under diesel scenarios. As noted
earlier, CTA bus facilities currently have significant state of good repair needs andoperate over capacity.33

Figure 14 – 2022-2040 Capital costs compared between scenarios

Within the electric scenarios, the more that fast charging is used (versus slow
charging), the lower the charger infrastructure costs, and differences in vehicle
purchase costs reflect different levels of growth assumed and accommodated byeach scenario, not any difference in technology or strategy. Facility upgrade costs arehigher under scenarios that accommodate more growth. However, these higher costs
to accommodate more growth should be viewed in the context that if they enable anincrease in bus service or reliability, this can yield further environmental benefits byattracting more trips that would otherwise be made via personal auto or similar lowoccupancy mode.

33 As discussed in Chapter 2e, it may not be essential to meet all state of good repair needs for bus facilities
before proceeding with electrification, however it is not possible to determine the division of essential and nonessential upgrades without the additional, more detailed, facility planning studies that have been noted as a
critical next step.
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51

Figure 15 shows that the estimated annual operating costs in 2040, once fleet
conversion has been completed, would be around $25 million lower for an electricbus fleet than a diesel bus fleet. This is due to the lower cost of electricity as a sourceof energy, compared to diesel.34 Conventional wisdom holds that electric buses canalso yield maintenance cost savings compared to diesel buses, however, longer-term
experience operating electric buses is needed to better understand the maintenancecost impacts over the full lifetime of a vehicle. As a result, this analysis uses CTA’s
experience to date and some additional conservative assumptions regarding electricbus maintenance costs to ensure we are not projecting savings that never materialize.35

Figure 15 – 2040 Operating costs compared between scenarios
Note that diesel fuel costs for heaters on electric buses are included, but the bar is very small.

34 Note that electric vehicles also tend to be significantly more energy-efficient than internal combustion
engines. U.S. Department of Energy, Office of Energy Efficiency & Renewable Energy. “All-Electric Vehicles.”
https://www.fueleconomy.gov/feg/evtech.shtml
35 The detailed cost assumptions can be found in Section D of the Appendix.
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52

Figure 16 – 2041-2048 Average annual capital costs comparison. An eight-year period is used to account for the annuallyinconsistent or “lumpy” nature of these costs.

The operating savings from a fully electric fleet is expected to be offset by ongoing
capital costs that are reduced compared to the transition period, but continue to be
somewhat higher than diesel scenarios even after the transition is complete. Figure 16
shows that the estimated annual capital costs after full fleet conversion, over theyears 2041-2048, would be around $90 million per year greater for an electric bus fleet
than a diesel bus fleet. This is due to the added cost of replacing chargers and the
projected higher costs to purchase and overhaul electric buses.
The results of this cost modeling point to several high-level conclusions and tradeoffs:• Overall, scenarios transitioning to an electric bus fleet would be $1.7 to $2.9
billion more costly relative to comparable diesel scenarios, for the combined
operating and capital costs evaluated over the 2022-2040 period. The range
reflects differences in scenarios with respect to charging strategies and thelevel of growth accommodated.
• The up-front capital investment to electrify the fleet is significantly higher
than maintaining a diesel fleet, and ongoing capital costs will remain somewhat
higher even after the transition. By the end of the transition, however, anelectric fleet will result in a modest operating cost savings that is expected
to persist.
• Using more fast charging at garages is projected to be significantly lesscostly compared to using more slow charging. However, as discussed in
Chapter 2d, concerns remain about the battery performance of fast-charged
buses, so more experience with the technology is needed before fully
embracing fast charging as the primary charging strategy.

CHARGING FORWARD | CTA BUS ELECTRIFICATION PLANNING REPORT53

• Converting outdoor garages to indoor facilities adds capital cost but
could facilitate more fast charging, which could generate savings that offset
the costs. There are also other benefits of an indoor facility for agency staff
and operations.
• Accommodating higher levels of fleet growth requires higher levels ofinvestment. The scenarios with the least investment in increased facility
capacity (Scenarios 1, 3, and 6) accommodate the least fleet growth, while
the other scenarios accommodate greater fleet growth. Fleet growth canbring improvements to the transit system as a whole, but because the level ofgrowth will be determined by other factors, separate from electrification (seepage 45), decisions about the appropriate level of fleet growth to plan for, andthe associated facility needs, will need to be revisited as trends evolve.

Projected Emissions
Finally, our modeling estimated the air quality and climate change benefits of pursuing
an electric fleet strategy compared with a diesel fleet strategy. This analysis considered
the local (tailpipe) emissions from buses, and the upstream emissions from generating
power used by electric buses. The specific pollutants we analyzed included CO2e,36
which contributes to climate change; NOx, which contributes to respiratory healthissues; and PM2.5, which contributes to respiratory and cardiovascular health issues.37
In addition to the power used by electric buses, some operational factors ofelectrification will also contribute to local and global emissions; these were includedin the modeling and offset some of the reductions. These factors included vehicle
block changes, which will require some buses to operate for additional distances toand from garages, using more energy from the grid; and heaters used to warm thecabin temperature during cold weather, which will continue to use diesel fuel andrelease some local emissions. However, modeling indicated that the impact of thesefactors is tiny compared with the overall environmental benefits of electrification.
The following graphs illustrate that, relative to the comparable diesel scenarios, theelectrification scenarios would reduce total CO2e emissions from CTA buses by 73%
and total NOx emissions by 98%. These reductions would not be immediate but would
develop over time as the bus fleet makeup shifts from diesel to electric. These benefits
accrue locally, regionally, and globally.

36 Carbon dioxide equivalent, or CO2e, is a metric that combines the emissions from various greenhouse gases
based on their global warming potential.
37 American Lung Association. What Makes Outdoor Air Unhealthy. www.lung.org/clean-air/outdoors/whatmakes-air-unhealthy
CHARGING FORWARD | CTA BUS ELECTRIFICATION PLANNING REPORT54

Results for PM2.5 show a somewhat different trend. Local PM2.5 emissions from CTA
buses would drop by over 99%, a clear benefit to Chicagoans. However, total PM2.5
emissions would increase by 33%. This is primarily because the electrical grid delivers
power generated from fossil-based sources including coal. In addition, newer diesel
buses have much lower PM2.5 emissions compared to older models, and it is projectedthat technology improvements will continue to reduce emissions further. It is possiblethat particulate emissions from electricity generation will decrease in the future as
more governments and utilities set targets for cleaner and more sustainable electricity
generation.

Figure 17 – Projected emissions of three pollutants under diesel scenarios and electrification scenarios

Overall, the reductions in climate-changing emissions and the reductions in local
health-impacting emissions are quite significant, and justify the cost increases over
the transition period that are summarized in the previous section.

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55

Focus: Grant Funding for Electric Bus Program

Thus far, CTA’s electric bus program has received
approximately $130 million in funding, primarily
through competitive federal grants from the following
programs:• Congestion Mitigation and Air Quality (CMAQ)
grants• Low or No Emissions Vehicle (“Low-No”)
grants• Diesel Emissions Reduction Act (DERA) grants• Illinois EPA “Driving A Cleaner Illinois” VW
Settlement grant
All of these programs have additional funds for future
grant rounds and will be important sources to support
CTA’s continued electric bus fleet and charging
infrastructure expansion. The recently-passed
Infrastructure Investment and Jobs Act also is also
expected to provide a significant increase in public
transit infrastructure funding compared with previous
levels. It includes funding for low and no emissions
vehicles and related infrastructure, funding for stateof good repair improvements, and greater opportunity
for federal highway funds to be transferred to transit
projects. These federal programs typically require
local matching funds, so the support of state and local
partners will remain important.

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56

Chapter 5. Conclusions
Based on the various analyses and findings summarized in thisreport, CTA has reached several important conclusions related to its
electrification approach. These conclusions address the following key
strategic questions that must be answered to plan for a transition to an
all-electric fleet by 2040:

Is CTA’s bus service compatible with electric bus
technology?
• Yes, all of CTA’s bus service either already is or can eventually becompatible with electric bus technology given anticipated technology
advances and a reasonable level of adaptation. While many of CTA’s buses
operate daily distances that exceed the effective range of electric buses on themarket today, CTA has several solutions available to address the remaining
bus service that is more challenging to electrify.
• With garage charging alone, 63% of weekday vehicle blocks and 21% of
Saturday vehicle blocks are already compatible with electric bus technologythat is newly available or coming to market soon.
• This means CTA has a lot of service that can be electrified before needing toaddress the service that is currently incompatible, but CTA will need to assess
technology and weigh options for increasing compatibility as the technology
develops.
• The primary options to increase compatibility are 1) modifying schedules by
splitting apart long vehicle blocks, and 2) adding on-route charging locations.
Both of these options add cost and have advantages and disadvantages thatshould be reevaluated after gaining more experience with the vehicle andcharging technologies. It is also possible that service compatibility could
be achieved by an accelerated advancement of existing technologies or
emergence of new technologies.

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57

How should CTA charge electric buses?
• The best charging mechanism for CTA is overhead charging using dropdown pantographs. This is a standardized and automated approach that canbe used both for slow charging and fast charging.
• CTA should centralize charging at garages to the extent feasible, rather thandeveloping an extensive on-route network of chargers. However, even withtechnology improvement, it is not likely that all service will be compatible withelectrification such that sufficient charging could take place at garages alone.
As a result, CTA should also develop a limited on-route charger network.
These charging installations should be targeted to high-usage locations that
benefit a large number of buses that would otherwise not be able to complete
their current scheduled service using electric vehicle technology. Minimizing
the number of on-route charging locations is important because they requiresignificant infrastructure investment, add complexity and cost to operations,and as technology improves, they will generally become less needed.
• At garages, CTA should initially implement a “Moderate Fast Charging”
strategy, which includes one fast charger per current fueling lane in addition
to slow charging for the balance of charging needed. This choice recognizes
that fast charging has the potential to generate significant cost savings, butalso hedges against the strategy’s potential technology-related risks. CTA canadapt this strategy as it learns from its first garage installations. If fast charging
technology and operations work well, and issues such as battery degradationand cold temperature impacts are manageable, then CTA may embrace a“Mostly Fast Charging” strategy to save on capital costs and reduce impacts
to storage capacity and overall layout at garages. Conversely, if significant
issues emerge related to fast charging, then CTA may choose to shift to moreslow charging at garages.

What facility improvements will be needed?
• Upgrades to electrical power infrastructure must be completed to support
the amount of charging that will be needed. This includes enhancement
and expansion of ComEd’s grid infrastructure as well as enhancement andexpansion of CTA’s own electrical infrastructure at its facilities. Each of CTA’s
garages is expected to need 5 to 17 MW of additional electrical capacity tosupport charging, depending on the scenario.

CHARGING FORWARD | CTA BUS ELECTRIFICATION PLANNING REPORT58

• CTA will need to install a significant number of chargers across its bus
garages: The “Moderate Fast Charging” scenario that is recommended
initially is estimated to require 500 to 600 slow charger cabinets and 30 to 40
fast chargers in total across all garages.38 This infrastructure is critical; electricbuses without the chargers to support them would be useless.
• CTA’s bus garages need various state of good repair improvements thatare independent of bus fleet electrification but must be coordinated withelectrification upgrades in order to be cost effective and support the new
infrastructure. Most significantly, three garages are in need of significant
modernization: 77th Street Garage, Forest Glen Garage, and North Park
Garage. The power upgrades and charging infrastructure required forelectrification should be coordinated as part of larger rehabilitation projects.
• South Shops, CTA’s heavy maintenance facility for buses located adjacent
to 77th Street Garage, also needs significant modernization, as well as the
addition of infrastructure to allow servicing of electric buses in parallel withthe diesel buses it will need to continue to serve until the full fleet conversion
is complete. This facility will be studied together with 77th Street Garage.
• Most of CTA’s bus garages currently serve more buses than they were designed
for; systemwide, there is an existing capacity deficit of over 200 standard
bus equivalents (SBE), which is essentially one garage’s worth of buses. This
causes garage operational issues today and will likely limit CTA’s flexibility toaccommodate sufficient charger equipment in suitable locations. Operationalchanges, such as the need to move buses around to charge at different times,
may also exacerbate the capacity issues that already exist. As a result, a
new bus garage is needed to provide adequate storage capacity. This will
alleviate current capacity constraints, ensure sufficient space for charging
infrastructure, and facilitate bus fleet conversion by providing an alternative
base while other garages are under construction.
• Depending on the mix of slow and fast charging that is ultimately pursued andthe degree of potential fleet growth that needs to be planned for, there is also a
potential need to increase storage capacity by reconfiguring Forest Glenand North Park garages, where CTA already owns adjacent properties andhas considered reconfigurations.

38 If CTA ultimately shifts to a different garage charging scenario, the number of each type of charger mayvary significantly; scenarios with more fast chargers require fewer slow chargers, and vice versa. Based on
our analysis, the full variation across all charging strategies systemwide is between 100 and 800 slow charger
cabinets, and between 8 and 60 fast chargers. Note that in all cases the slow charger cabinets are assumed tohave three pantograph dispensers each, and so be able to serve three parked buses each night.
CHARGING FORWARD | CTA BUS ELECTRIFICATION PLANNING REPORT59

• Forest Glen and North Park are also the only outdoor garages in CTA’s system,and outdoor overnight bus storage may have drawbacks with respect to fast
charging in particular. If these facilities are reconfigured to increase capacity,
replacing outdoor storage with indoor storage facilities at Forest Glenand North Park Garages should also be considered.

How should electrification be phased and organized?
• Based on CTA’s standard bus lifetime of 14 years, bus purchases will have to
be all-electric starting in 2026 to ensure that the last diesel buses are retiredby 2040. Some phasing in of electric buses before that date has already begunand should continue between now and 2026 to the maximum extent feasible.
• The sequence of garage upgrades and construction to support electric buseshas been developed based on prioritization of equity and considering the needto avoid overlap of multiple major projects. The planned garage sequence forbeginning electric bus implementation and charger installations is as follows:
1) Chicago Avenue Garage, 2) 103rd Street Garage, 3) 77th Street Garage, 4)74th Street Garage, 5) New Garage, 6) Kedzie Avenue Garage, 7) Forest GlenGarage, 8) North Park Garage.39 Planning work to address 77th Street Garage
and the South Shops heavy maintenance facility and for the new garage must
begin soon in order to meet these targets.
• Sufficient charging capacity must be planned to serve the electric bus
purchases anticipated for each year. Facility upgrades must also be plannedto accommodate the need to space out major renovation/construction
projects, which require more advance planning and funding, and which
necessitate temporary storage for displaced buses. Garages that are currently
in better condition may be upgraded incrementally over time to meet growing
charging requirements. For CTA’s oldest garages that require larger scale
upgrades, some facility rehabilitation work may be required in conjunction
with the electrification upgrades. In addition to these required upgrades, stateof good repair projects should be coordinated with the installation of new
infrastructure at bus facilities, whenever feasible, to avoid duplication of effort,
construction disruption, and associated cost increases.

39 Note that CTA has already installed a limited number of chargers at several garages to support the electricbus pilots.
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What are the benefits of bus fleet electrification?
• Bus electrification will reduce climate-changing emissions from busessignificantly. Compared to maintaining a diesel fleet, full bus fleet electrification
is projected to reduce total annual CO2e emissions by 73%.
• Bus electrification will nearly eliminate local health-impacting air pollution
from buses. Compared to maintaining a diesel fleet, full bus fleet electrification
is projected to reduce total NOx emissions by 98%, and local PM2.5 emissions
are projected to be reduced by over 99%. Overall PM2.5 emissions, inclusive ofregional and local emissions, are projected to rise by 33% unless the regional
grid’s mix of power plant fuel sources shifts away from coal and other fossil
fuels toward cleaner sources such as wind and solar.
• Although not addressed in detail as part of this study, converting to electricbuses also is expected to reduce traffic noise from buses compared withcurrent diesel buses.
• CTA’s plans for fleet electrification, and the associated public health benefits,prioritize improvements in historically disadvantaged communities
including low-income communities and communities of color.
• Pursuing a plan to electrify its sizeable fleet by 2040 will place CTA in aleadership role, driving advances in electric vehicle technology, especially forheavy-duty vehicles. It will also enable CTA to share knowledge and experience
with other agencies and fleet operators, help catalyze investments in the city’s
grid infrastructure, and promote vehicle electrification more broadly.
• Electrification is anticipated to generate long-term operating cost savings
from the lower cost of electricity as compared with diesel fuel. Somemaintenance cost savings may be possible as well, but longer-term experience
with operating electric buses is needed to confirm the overall impact onmaintenance costs.

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What resources are needed toachieve full electrification by 2040?
• Meeting the 2040 fleet electrification target
will depend on CTA receiving sufficientand sustained additional capital funding;electrification cannot be achieved at theexpense of service levels or overall system
state of good repair.
• The annual capital funding levels necessary toelectrify the entire bus system are significantly
greater than the historical funding that CTA
has received each year over the past decade.
Increased annual funding is critical to pay forthe higher cost of every electric bus, as well as
timely investments in charging infrastructure toensure that it is installed and fully operational
when CTA takes delivery of new electric buses.
Increased annual funding will also be needed
to cover crucial bus facility upgrades that are
most cost-effective and efficient to implement
at the same as charging infrastructure
installations. Ideally, greater funding levels
should enable CTA to adhere to the industry
standard of 14 years for the lifetime of a bus – aduration that CTA exceeds today due to lack ofsufficient capital funding.

“Meeting the 2040
fleet electrification
target will dependon CTA receiving
sufficient andsustained
additional
capital funding;electrification
cannot be achievedat the expenseof service levels
or overall system
state of good
repair.”• It is also important for CTA to have a reasonable
degree of certainty that recurring funding
will be consistent, long-term, and reliably
available according to the planned timeline, inorder to ensure that phased facility upgrades
and charging infrastructure installations arecompleted efficiently.

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Chapter 6. Next Steps
This planning study establishes a strategic framework for the electrification of CTA’s bus fleet by 2040. Much more work is needed to make thisplan a reality. This chapter sets forth several of the critical, specific next
steps to begin implementing this plan.
Pursue capital funding and intergovernmental support for electrification.
Significant additional capital funding, as detailed in prior sections, will be needed to
upgrade bus facilities and purchase electric buses and chargers as part of this plan.
In the near-term, additional capital funding is urgently needed to undertake concept
design and facility analyses for each of the bus garages; these are crucial thresholdsteps for the entire 18-year electrification process. This will require substantial
support, resources, and coordination from and with many public sector stakeholders,
including elected officials and relevant agencies at all levels of government. To theextent that agencies with jurisdiction can provide streamlined or expedited review,
permitting, and/or pre-approval processes for electric bus infrastructure, this will help
CTA adhere to its schedule for electrification. Coordination with Pace Suburban Bus
is ongoing, to ensure that the transitions of both fleets to cleaner vehicle technologies
are aligned and efficient.
Conduct outreach to educate, seek feedback, and build consensus around planelements. This would include outreach to explain CTA’s anticipated rollout of electricbuses, along with both the benefits of, and challenges to, bus electrification. It would
also include more targeted outreach to local community stakeholders and elected
officials to seek input regarding the potential local impacts and benefits of garage
upgrades or on-route charger installations. These efforts can help CTA refine plans
and build support for bus electrification.
Develop detailed facility plans and designs. The results of this study provide a highlevel guide to the number and type of chargers and sizing of power infrastructure thatwill need to be installed to serve a fully electric bus fleet, but more detailed facilityspecific planning is required. This includes finer-grained planning and design for eachof the seven existing garages and CTA’s heavy maintenance facility. It also includes

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siting, land acquisition, and environmental analysis for a new garage; finalization of
on-route charging locations; and comprehensive planning and concept design for allof these new facilities. At existing garages, this work will include further refined anddetailed analyses of electrical loads, exact positioning of chargers and buses within
the garages, preparation of specifications, onsite housing for new electrical equipment,
and selection of a smart charging management system. Detailed facility analyses willbe critical in identifying, at a garage-specific level, the upgrades that are essential
to ensure safe, secure, and reliable operation of new charging equipment – such as
repairs to roofs, paving, and mechanical systems. It is a particularly high priority for
CTA to begin the next phases of planning for the first garages in the transition timeline(Chicago Avenue, 103rd Street, and 77th Street), and to begin the planning process
for a new garage.
Continue coordinating with ComEd to design and implement power upgrades.
Once the required electrical capacity at bus garages and on-route charging locations
is confirmed through in-depth technical studies, CTA should continue working closelywith ComEd to complete these upgrades. The timing of these upgrades will be critical
as a prerequisite for installing the charging equipment that is required to achieve
CTA’s broader electrification timeline.
Continue providing additional staff training. While electric buses are not anticipatedto dramatically impact staffing needs, there is an ongoing need for additional training
for operations, maintenance, and facilities staff on the new technology, as well as somechanges to their responsibilities. Bus operators and servicers are already receiving
training to drive the electric bus models CTA has in service, properly position busesfor overhead charging, and follow electric bus and charger safety protocols. Vehicle
maintenance staff and electricians maintaining the new charging infrastructure receive
specialized training in topics including bus electrical systems, and diagnostics andtroubleshooting. Importantly, training must occur on a recurring basis to ensure that
CTA personnel gain knowledge and expertise in the most advanced electric bus andcharger technologies that CTA integrates into the fleet and installs at bus facilities.
All training, staffing, and position scoping needs have been and will continue to becoordinated with employee unions.
Plan for risk and resiliency. Shifting the source of power for CTA’s entire fleet of
approximately 1,800 buses brings a host of changes that translate into shifts in risk; forexample, the risk of diesel price fluctuations or diesel supply chain interruptions will
become less important, but the risk of power outages becomes much more important.
Since CTA’s rail system has been powered by electricity nearly since its inception, there

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is significant agency experience with the associated risks of electric power supply. As
exists across CTA’s rail system today, CTA plans to ensure back-up power sources areavailable for charging infrastructure. CTA and other transit agencies are exploring thepotential for onsite power generation and microgrids, which could be considered as
options for back-up power. Electric buses, like all buses, are tested thoroughly before
deployment in regular service. Further analysis is needed to plan for the full array ofrisks associated with scaling up the electric bus fleet and to develop solutions that
ensure resiliency.
Adapt the bus electrification plan based on service levels and funding. The levelof need for fleet growth over the transition period will become clearer over time andshould inform refinements to the plan. Additionally, if the funding needs describedin this report are not met, whether in terms of timing or magnitude, the bus fleet
electrification plan and associated timelines – especially for bus facility upgrades –will also need to be adapted to fit the available funding.
Monitor the performance of technology and refine plans accordingly. The analyses
in this plan use the best data available on the performance of electric bus technologies.
However, as CTA and other transit agencies gain more real-world experience withelectric buses and chargers, plans should be re-assessed and modified as necessary.
For example, if the practical range of electric buses is demonstrated to be longer than
we have assumed, electric buses may be able to serve longer vehicle blocks thanshown in our current analysis. As noted elsewhere, close attention should also be given
to the impacts of fast charging related to battery degradation and the performance of
outdoor-stored buses. CTA will also monitor the evolution of other emissions-reducing
transit technologies, such as hydrogen fuel cell buses, to consider whether and how
these play a role in achieving bus system emissions reductions.

The Charging Forward study has allowed us to evaluate a range of potential
electrification strategies, yielding insights that will be invaluable as we develop more
specific plans and projects that advance our bus fleet towards full electrification. CTA
is eager to ramp up our deployment of electric buses while continuing to refine aspectsof our electrification strategy. We look forward to working together with partners andstakeholders to make this plan a reality.

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