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Zero emissions buses and the energy transition: How do transit agencies adjust facilities?

June 13, 2023

By Ryan Odell

ZEBs are a huge part of transit’s future. But battery electric and hydrogen fuel cell buses require unique OMSF designs. What are the key factors?

When you hop on the bus to get to the office or run an errand across town, you might be riding a vehicle that runs on hydrogen, electricity, natural gas, or old-fashioned diesel. Maybe you’ll know from the sound of the bus or maybe the vehicle will be labeled with its low-carbon status. Maybe you won’t notice at all.

But whatever type of bus you’re riding in, you’ve got a front-row seat for the energy transition. Mass transit is moving away from conventional fossil fuels.

The agencies that run these buses—which includes scheduling, cleaning, fueling, maintaining, and repairing them—are on the cusp of energy transition. They’ve been tasked with upgrading and maintaining their fleet while delivering service in an environment of rapid change and uncertainty.

The goal is to provide low carbon transit with performance that can still meet the needs of their community members. And for many that means converting the fleet to zero emissions buses (ZEBs). Often, they are using battery electric buses (BEBs) or hydrogen fuel cell electric buses (FCEBs). Aside from the fleet of buses itself, they’ll need operations, maintenance, and storage facilities (OMSFs) for the new fleet. They’ll need to do this all while running the old buses, too. Sound complicated? It is.

Stantec designed the new electrical system for the Anaheim Transportation Network Battery Electric Vehicle and Bus Charging Infrastructure in Anaheim, California. It provides power to the 100 new bus and vehicle chargers as well as the new building and ancillary yard loads.

FCEBs and BEBs are new technologies that have changed dramatically in recent years. It’s critical that agencies make sound decisions based on the fleet they are investing in. These include decisions about the infrastructure they will need to store and maintain the fleet.

The long phase-out

Fleet procurement is a phased process. It’s likely that agencies will run combination fleets with buses of different fuel types as they navigate their way to ZEBs over 20 to 25 years. While investment in new transit infrastructure is ongoing, a new OMSF should be designed to last 50 years or more. If transit agencies build new OMSFs, how do they allow for this period of transition? If they undertake a phased renovation, what are their considerations? What aspects of facility design can accommodate their changing fleet?

Determining fleet mix

The fleet moves people, and the facility serves the operational and maintenance needs of the fleet. The more we know about what the fleet will look like tomorrow, the better positioned we are to design or retrofit the facility. But projections can and will change over time. Thus, we need to understand the range of possibilities in the magnitude and rate of fleet growth and potential fleet types. Then we can design flexibility into the facility to mitigate risks from a changing fleet mix.

We can even help our agency clients discover what that optimum fleet mix might be. We examine the pros and cons of current battery electric versus hydrogen fuel cell technology. We can help agencies evaluate different technologies and see what suits their goals.

Here are some areas that transit agencies should consider for bus facility design in this period of energy transition that will enhance functionality and use for the next half century.

Site selection

Where should agencies locate their future operations and maintenance facilities for this transitional era?

They need to consider both infrastructure and operations. They will need to make sure they allocate space for electrical infrastructure (substation and transformers) and/or hydrogen power infrastructure (storage and possibly production) and back-up power (generators or storage). If they’re going electric, they will need to consider the local electric grid capacity and source (how clean or dirty). If they’re going with FCEBs, they’ll want to know what the regional source for hydrogen is and how it can be transported to the site.

However, the more suitable locations from an infrastructure perspective may not be ideal for their operational needs—such as route planning.

The TriMet Powell Bus Administration, Operations, & Maintenance Facility in Portland, Oregon, was designed to charge up to 60 buses with an expansion to 345 buses.

Electrical service needs, power needs

Obviously, BEBs will need chargers, which bring their own complexity and design considerations: Can existing structure handle the additional weight of chargers? What kind of clearance do they require inside? And most critically, where is the infrastructure for the increased electrical load? How does power reach the chargers?

Battery electric bus facilities draw enormous amounts of power. They require their own substations, either on- or off-site, which require their own planning and space. Agencies will need guidance on how to make room for electrical infrastructure, which may need to enlarge over time as the charging demands of the facility increase.

But the complexity doesn’t end there. Adding new power lines or connecting to multiple substations adds additional risk to these projects. It brings in associated regulatory complexity, capital costs, and the challenge of aligning third-party timelines with design and construction timelines for on-site infrastructure.

Hydrogen presents a different challenge regarding supply. Does it arrive on site via pipelines or tube trailers? Is it produced on-site, in the region, or farther away?

Indoor or outdoor fueling, storage, codes, and standards

When it comes to fuel storage, we need to talk about codes and standards.

For FCEB facilities, the agency needs to store hydrogen fuel to maximize safety. Site location and facility layout come into play. Even electric bus facilities will likely need to accommodate some diesel fuel for auxiliary heating on BEBs. For facilities maintaining multiple types of vehicles, codes and standards can get quite complicated. This impacts the electrical, mechanical, fire suppression, structural, and architectural aspects of the building design.

Size, warehousing, and layout

The mix of bus types and the size of the fleet the agency plans to maintain will influence the overall layout of their maintenance bays. This will also influence the size and configuration of the warehouse to support maintenance operations.

The transit agency will want a facility that is laid out for efficient flow and flexibility. Fleet size and mix, along with related inventory requirements, can change or grow over time.

The more we know about what the fleet will look like tomorrow, the better positioned we are to design or retrofit the facility.

Maintenance intensity, access, and equipment

Agencies typically target a bus-per-maintenance bay ratio based on their fleet composition, age, and other factors. Industry experience shows that maintenance intensity for BEBs tends to be lower than for diesel—which would suggest a higher bus/bay ratio for new facilities. But agencies transitioning to ZEBs may want to play it safe and build to the lower bus/bay ratios to maintain maximum flexibility.

Diesel, electric, and hydrogen buses are serviced very differently. EVs have few moving parts compared to a diesel or compressed natural gas bus, for instance. This has impacts on the compatibility of the maintenance shop and its equipment.

In a maintenance facility, it means different design criteria regarding the pits, vehicle lifts, and catwalks that technicians use to work on the vehicles, which have serviceable elements in different places based on vehicle type. So, facilities hosting a mix of vehicles may need multiple configurations of maintenance bays and/or flexibly designed bays that can host a range of fleet types.

The same goes for the industrial equipment the service technicians use. Different bus types have different lifting points. Heavier buses that are frame-lifted may require designers to specify in-ground hoists. The agency needs to look at the existing industrial equipment in the facility. Are the hoists compatible in terms of horizontal travel, weight capacity, and lifting points? Can they be adapted to the new fleet while they continue to serve the existing fleet?

Workforce development

Historically the facility technicians work on engines, transmissions, drivetrain, and other elements of gas or diesel bus engines. In this transition, those jobs gradually go away.

Servicing electrical systems and motors requires a different technical skillset. The short-term challenge for transit agencies is this: retraining or hiring and training the workforce to service the changing maintenance needs of a transitioning fleet. The long-term change: maintaining a large fleet of likely hundreds of electric buses.

Will there be a sufficient, trained workforce to maintain a larger electric fleet? Agencies need to plant the seeds on the educational side to grow that trained workforce to support their growing zero emissions fleet.


Extreme weather events and their associated power outages threaten the resiliency of an all-electric fleet. Transit providers need to ask themselves some serious questions. What kind of outages—in terms of magnitude and duration—do they need to protect their service from? Do they want back-up systems to power all their buses during a 4-hour power outage? Or just a few buses for 24 hours? Will hardening the immediate (micro) grid provide the resiliency they need? How much resiliency is enough? How much and what kind of energy do they need to store for emergencies?

In the short-term, while they have fossil-fuel vehicles in service, the non-ZEB fleet may serve as the backup. In the longer term, backup for ZEBs may take the form of energy storage systems, backup generators (diesel or natural gas), or hydrogen fuel stored on site. The latter will require sufficient backup electrical infrastructure to dispense hydrogen.

The Santa Monica Big Blue Bus Battery Electric Bus Charging Infrastructure project in Santa Monica, California, is helping the agency transition a 195-bus fleet to battery electric buses.


When equipped with the right technology, the buses in the fleet of tomorrow will be scheduled by software. Everything from their charging to predictive maintenance, as well as their route planning, entry to and exit of the facility will be kept on an automated schedule.

Facilities will need the right Wi-Fi coverage, bandwidth, and on-site systems to facilitate this kind of data-driven automated operational planning. The automation will need to play nicely with the physical environment of the facility. Agencies should understand that they’ll need to invest in IT to run their fleet on this technology.

Looking to the future

With these factors in mind, transit agencies can and will adapt or build their bus maintenance facilities to handle what is sure to be a long and challenging—but very important—transition to ZEBs. 

  • Ryan Odell

    As a market leader with our Operations, Maintenance, & Storage Facilities team, Ryan is passionate about creating quality spaces that help increase productivity and promote health and safety.

    Contact Ryan
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