Santa Barbara MTD is revamping its transit facilities master plan and planning its transition to BEBs in order to meet the goal of being 100% zero emissions by 2030. Stantec

By Sasha Pejcic, Analy Castillo, Peter Chatoff, and David Verbich

Zero-emission buses (ZEBs) are finding their place in transit circles by offering the opportunity to shift away from fossil fuel-powered bus fleets, whether through government mandate or as an agency-driven plan. ZEBs reflect a global trend to modernize fleets, reduce greenhouse-gas emissions, and make public transit a cleaner, friendlier transportation option. 

There are two types of ZEBs: Battery Electric Buses (BEB) and Hydrogen Fuel Cell Electric Buses (HFCEB). There’s a lot more to integrating either of these technologies into a transit fleet than simply buying a different kind of bus — it involves a systematic shift in the way a transit agency operates. As a result, some early adopters have found challenges in balancing a large-scale operation and high-quality service. 

Electric bus charging station. INIT

Electric bus charging station.


Agencies that decide to make the move to ZEBs must manage at least two types of propulsion technologies until the transition is complete, which could take a decade or more. The procurement process will take on a new level of strategy, as infrastructure will have to be roughed in with scheduled capital expenditures. Parts, fluids, and warehouse support will all need to be evaluated, and staff trained in relevant technologies including both legacy and ZEB propulsion. As a result, the era of ZEBs may bring fleet operators much closer to senior management levels as operations become more vertically integrated. Transit agencies will need to become more adaptable and flexible to bring their game-changing technologies on board.

As any agency weighs their decision to transition to ZEBs, there are some key considerations for them to review: procurement, financial, regulatory, and maintenance — for any agency to make as they weigh their decision to transition to ZEBs.

1. Procurement
As mentioned, there’s a lot more to bringing ZEBs online as part of a bus fleet than purchasing a different type of vehicle.

  • The maintenance and service needs of diesel or compressed natural gas (CNG) buses versus ZEBs are significant. For example, given current battery technology, a BEB-only fleet could be as much as 15 to 20 percent higher than that of a fossil fuel fleet. This is to accommodate the downtime buses need to charge batteries and their range capacity.
  • On some routes, BEBs may need to be switched out by cover runs so that they may return to the maintenance facility partway through the span of service in order to charge up if on-street charging infrastructure and routines are not part of an agency’s power strategy. This could also have a significant impact on planned route expansions or updates and driver scheduling to avoid downtime.
  • Another consideration is choosing a supplier for the ZEB fleet. ZEBs are still relatively new and going through some standardization codes and processes. While HFCEB already have this in place, BEBs still have different types of plugs for charging in the US and Canada. The SAE-J1772 and SAE-J3105 versions  are emerging as candidates for plug-in and pantograph charging standardization, so agencies should keep this on their radar to avoid investing in proprietary charging infrastructure that only works with a particular fleet.
  • In addition, few transit agencies to this point have developed custom ZEB procurement specifications. Rather, “off-the-shelf” ZEBs are being purchased that may or may not have common parts with legacy propulsion types. This brings the additional potential burden of managing more parts at their facilities which may already be constrained for space. Transit agencies are best served when they have common parts across their entire fleet and should request parts cross-reference lists at time of ZEB purchase. More on parts in the maintenance section.
  • One solution to simplify the procurement process is selecting one vendor under a multi-year agreement. Technology compatibility will be less of an issue on initial start-up, while making the learning curve for staff significantly easier. The agency will also have a better understanding of operational needs and solutions, without the added stress of trying to make different pieces work together. Additionally, this offers the ability to build an in-house inventory for common parts.
  • Parts distribution capabilities for ZEBs is continuously improving but at present transit agencies need to program additional time for specialized ZEB parts to arrive at their facilities. Transit agencies should carefully monitor component failures of their new ZEB fleets in order to establish preventive maintenance (PM) programs and proactive changeout campaigns based on failure trending and root-cause analysis.

Establishing performance metrics and metrics for vendor support can be valuable for managing procurement, documenting progress, and making informed decisions down the line.

2. Financial
The cost of ZEBs may present a challenge — BEBs are roughly twice as expensive as diesel buses and HFCEBs are about four times. This obviously has a capital expenditure impact, but it will potentially impact insurance premiums for the fleet.

  • Since the value of the asset is twice or four times as costly to replace, insurance companies will seek to mitigate that financial exposure. This has been evidenced with electric vehicles in the European automotive insurance industry.
  • The additional expense of licensing more vehicles and performing time-based mandated safety inspections needs to be considered.
  • There are also significant infrastructure needs to be addressed — facility improvement or enlargement, charging infrastructure, and power access, to name a few.

When planning for the financial impacts of ZEB integration, transit agencies can match infrastructure spends with scheduled procurements, maximizing efficiency, while avoiding overinvesting in infrastructure.

When planning for the financial impacts of ZEB integration, transit agencies can match infrastructure spends with scheduled procurements, maximizing efficiency, while avoiding overinvesting in infrastructure.

  • Having a proactive plan and roughing in infrastructure as part of capital procurements is an effective approach to balancing these different needs.
  • Additionally, such financial planning should be made throughout the life span of the vehicle, e.g. Total Cost of Ownership (TCO), to capture midlife  replacement for the batteries (sometimes included in the purchase price by certain manufacturers or addressed through leasing schemes) and to reflect savings related to decrease in the maintenance cost  such as fluid and filter changes and corresponding funds tied up in inventories.
  • On ZEBs, the only maintenance related to moving parts are from the cooling systems, and initial performance results suggest ZEBs have slower tire wear relative to fossil fuel propelled buses.  

3. Regulatory
While some regulatory impacts of ZEBs — like hard-and-fast spare ratios — are still being developed, there are existing requirements that will need to be approached differently.

For example, drivers cannot exceed a certain number of hours worked in a day. If buses need to return to the maintenance facility partway through their route for recharge, then driver changes, shuttles, and route planning will have to be integrated accordingly. Some of these issues may relate to collective agreement language and operating practices.

  • Each state and province also has its own inspection rules, which in many jurisdictions need to be managed and executed by licensed skilled tradespeople.
  • Having access to staff or contractors that make the fleet compliant with regulations is a core part of any agency’s mandate and needs to be considered from day one.

4. Maintenance
Irrespective of propulsion type, a transit agency with insufficient buses to meet pull-out is one that is of no use to its customers. Without a doubt, there will be challenges in the introduction of new technology.

  • One of the largest items is the phase-in period and transition from one propulsion technology over to the other. With typical heavy-duty bus life cycles, the term of transition could exceed a decade.
  • Maintenance personnel will need to be conversant with both propulsion types and as well all operating personnel will need to be trained and stay qualified on both.
  • When a different bus model, regardless of propulsion mode is introduced, parts unique to that model (as they may differ from current models in the fleet) will need to be procured and kept on hand. Parts Room space will be impacted. Parts associated with the new propulsion may also have to be added.
  • Over time, the old propulsion parts will decrease in need and space will be recovered. Once the transition is complete, the overall inventory should require less space.
  • Propulsion-oriented fluids (e.g. transmission oil) will decline in use and eventually disappear. If the new propulsion vehicles happen to be the same make and body style of the older vehicles on hand, some economies may be realized (e.g. windshields). When transition is complete, disposition of redundant inventory may have to be done.


A decision between plug and overhead charging will need to be made when considering electric bus infrastructure. Proterra

Maintenance routines will transition. Distance- or time-related routines associated with propulsion-based fluid and filter changes will diminish and eventually disappear. New inspection routines with the new propulsion will emerge. An impact on shop routines, scheduling and staffing and labor hours in the shop will occur. It is a fact that regenerative braking, already apparent in diesel-electric hybrid buses will expand the distance between brake reline events. This will save downtime and labor/material costs.

External business practices may also change. Depending on resources and size and established routines, maintenance/shop routines and collective agreements, shop routines and contracting out maintenance/repair functions may be impacted.  For example, heavy engine rebuilds sent to OEM dealers and jobbers would diminish and then disappear.

  • Infrastructure and layout for charging equipment will need to be laid out, procured and installed in the most operationally efficient manner.
  • A decision between plug and overhead charging will need to be made.
  • Service line routines will lose the refueling and fluid checks but other activities such as interior sweeping and mopping, exterior washing, and farebox emptying will continue but perhaps in another format.

These changed routines will affect associated personnel and parking arrangements. Again, the transition period will be dynamic with changes occurring over a period of time in tandem with the fleet propulsion profile.

The battery-electric buses will no doubt be charged after the daily servicing function. The hydrogen fuel-cell buses will no doubt be “refueled” at the servicing point but with a greater elapsed time than diesel buses considering that hydrogen fuel tanks need time to re-pressurize.

  • Once the ZEB type vehicles are ready for service, battery health (or State of Charge - SOC) may have to be verified to ensure they are ready for service prior to drivers arriving to do their pre-trip inspection.
  • Finally, dispatching and vehicle parking placement will be somewhat more complex and bus assignments may become more route and run specific depending on range and run mileage factors.

Once the transition to the new propulsion is completed, and the ZEB type vehicles mature in technology, the complexities may decrease.

  • In addition to maintenance staff, operations staff (e.g. dispatchers, on street supervisors, control room personnel) will need to be more conversant with specific vehicle characteristics to avoid service disruption.
  • Careful scheduling of runs and routines and coordination between operations and maintenance staff will be more critical such as in having vehicles coming into the facility for mid-day charging between the rush hours.

Moving public transit into the future
ZEBs provide an opportunity to shift technology and workplace culture, but also the agency’s relationship with its customers. Taking action to integrate a clean, quiet, sustainable fleet of service vehicles makes a statement on the commitment of the agency to a positive transit experience and contributing to more sustainable communities. These attributes can serve to grow the ridership level, which in turn, can increase the proportion of farebox recovery towards operating costs.

Taking action to integrate a clean, quiet, sustainable fleet of service vehicles makes a statement on the commitment of the agency to a positive transit experience and contributing to more sustainable communities.

This statement can be leveraged to paint a new image for transit in the city — through refreshed branding, a fresh coat of paint, or upgraded uniforms. Bringing ZEBs online communicates a shift in values, and that shift can be communicated in other community-building ways as well.

From a macro level, we see ZEBs as an opportunity to reinvigorate the concept of public transit in a way that meets the values of younger generations and “transit greening” priorities. Integrating ZEBs into transit fleets certainly presents some challenges, but the benefits to operations and to the agency as a whole are worth consideration.

Sasha Pejcic is managing priciple/transit advisory lead; Analy Castillo is transit advisory consultant; Peter Chatoff is sr. transit technologist; and David Verbich is team lead/transit advisory with Stantec.