Agencies that have a combination of express suburban, line hall, circulator, and bus rapid transit services must account for them all in their ZEB deployment choices. - IndyGo

Agencies that have a combination of express suburban, line hall, circulator, and bus rapid transit services must account for them all in their ZEB deployment choices.


Like the first rocket launch, everything about converting an entire industry to operate on zero emission propulsion is daunting. And it’s not as though public transportation has avoided hard technological challenges; indeed, the list of transitions that transits have undergone, from rapid rail expansion after many decades of post-World War II decline, to near-zero emission operation with ultralow-sulfur diesel hybrids and natural gas buses, have been achieved, albeit with the “teething pains” that come with the adoption of new technologies.

This revolution is very different. Earlier ones did not have to depend on so many outside forces for success. To convert to zero emission also means a clean, stable, smart grid and available trained staff who can handle high voltage equipment. We’ll get into the six fundamental challenges transit faces in this revolution — and the word is used deliberately here, for it is not an evolution from how far and fast the industry has already come. We’ll also cover rail’s contribution here (see sidebar). Finally, some keys to success will be examined.

These observations are from the experience of one who is deeply involved in these programs and one who has observed and tracked previous technological changes for four decades. These findings have deliberately avoided using names and specific case studies to make these larger points; these experiences include working with many who are engaged in these transitions or face governing boards and state agencies eager to make the leap. They will undoubtedly be nodding their heads in acknowledgement.

6 revolutions within the ZE revolution

Pick your metaphor: transitioning to zero emission vehicles is as complex as anything ever undertaken by this industry. All six different major technological and logistical transformations – six nested dolls in one of those Russian sets, or six onion layers — must be successfully addressed in every ZE transition program. Here’s another metaphor: they all must be addressed simultaneously in a choreography every bit as intricate as anything performed on Broadway.

Moreover, each of these challenges increase with complexity — exponentially, in fact — as the fleet and agency size gets bigger. Although fleet size and budgets are the obvious differences between large and small operators, the complexities of the challenges of transitioning larger fleets to 100% zero emissions are often multiplied. Power requirements, infrastructure constraints, blended fleet management, and lengthy program phasing across multiple sites are much more complex with larger fleets. I have led such projects for both large and small fleet operators; how these projects scale in their challenges is essential to understanding the towering challenges that public transportation faces as a whole.

The first of these six challenges is the one most discussed: geography. The location, size, and shape of the geographic and built environments in which buses — and, increasingly, rail (see sidebar) — operate matter significantly. Of course, seasonal differences affect energy performance throughout a year, especially in those places with seasonal extremes. 

The variances in conditions that need to be covered as size of the service area gets larger is perhaps the less-mentioned aspect of this first challenge. For example, larger service areas likely to have more topographic changes that have effects on these consumption rates. Regenerative braking, which is typically a feature of propulsion systems that depend on electric motors, help to recapture some of the energy lost on the climb as the vehicle starts its way back down again, but it doesn’t recapture all of it. 

Sometimes microclimates, where hot, more humid parts of a region — or conversely, colder, wetter, or drier, parts — will have very different energy consumption rates, due to heating and air conditioning systems, but also the braking, acceleration, and speed rates caused by climate and road conditions. Even neighborhood differences in the built environment, such as those with more intersections or more walkable neighborhoods, have different effects. 

Network complexity complicates planning

A second, related challenge is the complexity of the route network itself, which typically grows dramatically with fleet and service area size. Agencies that have a combination of express suburban, line hall, circulator, and bus rapid transit (BRT) services must account for them all in their ZEB deployment choices, which typically also comprise a mixed of bus models and types. Not only do changes in stop distances and frequencies on each route alter vehicle performance, so do variances in passengers boarding and alighting, because these differences affect gross vehicle weights and the cycling of the doors during each day of service. 

To perform these transitions without service disruptions, new facilities to replace the old — a more expensive choice — or planned in stages, often with temporary moves to other depots — less expensive capital costs but more expensive operationally and involving far more intricate planning. The Broadway production now turns into a series of dances performed by a repertory company; again, more intricate as the operation gets bigger. And all choreographed and completed before the buses are delivered (the third challenge, to be discussed momentarily).

To address these first two challenges, agencies should rely on good performance modeling of their routes and service areas. In addition to modeling the entire service network, these simulations should account for the weekday, weekend, and seasonal ideally rare events such as weather extremes or special event services. Furthermore, such good modeling should be compared against data derived from trial demonstrations of bus models that are of interest; the data from those runs can provide some insights into how good the modeling must be. Finally, it is important to plan ZE transitions based on some of the most extreme conditions that agencies encounter, such as crush loads on some of the toughest topographies, on congested routes, and some of the coldest and hottest days recorded in the service region. 

This might seem like overkill, but some of the most common transition mistakes have been failures of imagination, such as overconfidence in the Altoona results or projections for full transitions of fleets, services, and facilities based on an agency’s battery-electric/fuel cell bus pilot programs. More than a few charging installations at garages have had to be redone because they were not “future proofed” for when the whole depot would be retrofit for chargers or hydrogen fueling facilities.

Vehicle availability and supply chain getting better, but more is  needed

Third challenge, the availability of the vehicles in the market — and related, their builders’ supply chains — is becoming an increasing challenge to transitioning to an all-ZE future. This is not to say that the supply chain isn’t growing; it is, as more manufacturers enter the transit marketplace with a growing list of vehicle models. In addition, more established manufacturers are expanding their operations as demand grows. These issues have additional dimensions for larger fleets, because they typically have more legacy vehicle types and technologies to replace with ZEBs.

However, two other issues have also complicated vehicle challenges, worsened by the onset of the pandemic and by national politics that have become increasingly concerned about international economic threats, especially from China. The first of these is supply chain shortages and vehicle delivery delays, as logistical and workforce disruptions have brought havoc on production schedules. Buy America concerns and Chinese rolling stock bans have also complicated these concerns, leaving agencies with fewer choices.

This is especially important in the battery supplier market. As was recently pointed out in a Calstart report, China has 90 EV battery manufacturers and has invested more than $10 billion in government subsidies in the past decade. South Korea and Japan also have strong battery industrial policies; even such countries as the Czech Republic, Poland, and Hungary have vehicle battery manufacturing. While U.S. investment increased in recent years with 10 major battery factories located in the country by 2030, it is insufficient, especially because other surface transportation sectors are also transitioning to ZE vehicles.

The final three are toughest

We’ve seen the industry overcome technological shifts many times before — yet the three most vexing for ZE transition have been saved for last here. The fourth challenge, also increasing in complexity with scale, is labor related. These issues range from training of existing staff to accommodate these new vehicles to recruitment of managerial staff. This has been made even more complex as the industry grows and a generation of Baby Boomers are retiring at increasing rates. 

Workforce needs have been on various APTA and Eno Foundation agendas for nearly a decade. Recruitment initiatives are even reaching into middle and high schools. All must be ramped up with massive training grant assistance, because the unfamiliarity with dangerous high voltage equipment. This could be one area where multimodal agencies do have an advantage over smaller agencies, if “train the trainers” programs can be organized with rail technicians teaching their bus counterparts. 

The fundamental impacts of electrification comprise the fifth challenge. Whether adoption of fuel-cell buses or battery-electric propulsion, the revolutionary nature of this transition means a dependence on a wholly new source of propulsion and related support industries. Larger service areas typically mean that more than one utility must be fully engaged in discussions to provide service upgrades at multiple maintenance depots and often at layover facilities on the route networks. Regardless of the number of utilities, the available power that the circuits that must serve these facilities varies, sometimes widely. 

Even many utilities are surprised by the amount of power that a rather average size of bus depot must demand, which at more than 15 megawatts at peak usage can exceed that of a skyscraper or medical center. Even when the power demand is optimized with charge management technologies, it can still easily exceed five megawatts at times throughout a service weekday. So-called vehicle-to-grid or vehicle-to-infrastructure technologies also look promising, but they are nascent to date in the heavy-duty vehicle markets.

Many agencies are looking at microgrid strategies that either store power from solar or wind sources for peak demand needs or from the grid during low usage times. These strategies could be limited by metering constraints imposed by the local utilities, which can drive up capital costs. Investor-owned utilities are especially concerned by these ideas because their pricing and investment strategies must be vetted not only by state regulatory authorities, which take time, but by their investors and the bond rating agencies. Fortunately, microgrid strategies can make economic sense to both the utilities, as well as the transit agencies, but such planning also takes time.

Some agencies see hydrogen fuel cells as the answer that solves range anxiety and power issues in these transitions. However, this option has challenges of its own, including limited suppliers, less bus manufacturer experience with fuel cells compared with battery electric propulsion, and limited hydrogen supplies. To address the last point, hydrogen suppliers can either choose to procure reformed hydrogen from natural gas or from electrolysis, which involved electric power from the grid or renewable sources. Then there are the demands that these supplies will place on shortages of potable water, especially in the western U.S.

This is not to say that only hydrogen has these complexities. Sourcing of materials to make batteries, such as cobalt and lithium, are often mined in unstable parts of the world using unsavory labor practices. Disposal of batteries is an equally vexing concern, which is why many agencies shift liabilities of disposal and custody to the bus and battery manufacturers.

The final and sixth battle that must be fought is cost. As the Center for Transportation and the Environment (CTE) recently concluded in its work for the House Transportation and Infrastructure Committee, $56.22 billion to $88.91 billion above baseline levels will be needed to transition the rest of the transit bus fleet to zero emission by 2035. Billions more will be needed to transition diesel-powered rail transit vehicles to electric propulsion.

Those estimates might have been optimistic, because some parts of those costs did not include the FTA’s standard cost categories of insurance and allocated and unallocated risks that comprise any capital grant request. Nor did it account for escalation that will be necessary, because the committee’s question to the CTE report was what it would cost if it could fund such a program by 2035.

Help likely to be on the way

This is not to say that this transition cannot succeed despite these six challenges. Some agencies already have made the transition, and those are the case studies that must be examined in detail. Moreover, some innovations and additional funding are in the works to help the cause.

One such answer could lie in the aforenoted technologies that allow vehicles to give power back to the grid, buildings, or some energy storage device. Many smaller electric vehicles already have this capability, and because the technology is especially attractive to the medium-duty truck markets for such applications as delivery and school bus fleets, which use the same platforms as trucks, they might also help with paratransit and other service applications where smaller buses make more sense. 

Additional help might also be coming in some transformational funding. At press time, voting was scheduled in the House on the bipartisan infrastructure legislation that has already passed the Senate. If this is signed into law by President Biden as is presumed, it could be hundreds of millions of dollars in funding for a range of ZE projects, from the technical assistance described above to historic investments in ZE fleets to grid modernization programs, beginning as early as next year. And this is excluding the climate change mitigation measures that are included in the $3.5 trillion reconciliation bill, which remained a possibility at press time.

The way forward

None of these six dauting challenges described herein is to say we should abort this journey. We cannot. The climate and a more secure world (the Pentagon’s words, not this author’s) depends on this transition, and the transit industry is arguably one of the smaller players — though ones no less important — engaged in this revolution. It might be that the pace of the transition must slow a bit here and there, depending on circumstances and forces beyond the industry’s control, but it must continue to move forward, for the benefits of doing so continue to increase while the costs continue to near a parity with the status quo over the next decade.

It is, rather, to say we must do as what progress always demands: learn from setbacks, avoid repeating mistakes, secure the needed resources, and above all, continue.  

We must think of this massive transformation as the industry’s race to the moon. Like President Kennedy’s May 1961 challenge to land men on the moon before the decade’s end, transit is embarking on similarly ambitious goal. Yet unlike the space program, which had only just put America’s first astronaut, Alan Shepard, barely into space with very little idea of how it would accomplish the moon mission, some transit agencies have already completed a full transition to electric propulsion. How they got there and how they are faring becomes the next chapter in this story.

“We choose to go to the moon in this decade,” President Kennedy said the following year, “because that challenge is one that we are willing to accept, one we are unwilling to postpone, and one which we intend to win.” Words fitting for this moonshot as well.