Managing the Mix

March 13, 2020
In the first of a two-part series looking at mixed bus fleets, three agencies outline how their strategies and best practices ensure service levels are maintained as they move through their fleet transition plans.

Today’s transit fleets consist of vehicles powered by a variety of different fueling and propulsion systems. The transit industry’s focus on sustainability makes the evaluation of battery-electric and hydrogen fuel-cell buses an inevitable outcome while the availability of federal grants for low and zero-emission buses provides funding to aid in the exploration of these and additional technologies. Further pushing the fleet transition are local and state mandates, such as the California Air Resources Board’s (CARB) approval of a regulation in December 2018, which sets a statewide goal for public transit agencies to gradually transition to 100-percent zero-emission bus fleets by 2040. Solano County Transit, Orange County Transportation Authority and Foothill Transit are three of California’s transit providers working to meet this deadline. 

While a fleet’s mix can impact how a system manages its operations, it should not impact the service provided. Ultimately, riders want to reliably arrive at their destinations and do not care if the bus that takes them is powered by diesel, compressed natural gas (CNG), batteries, hydrogen fuel-cells or other systems.


Solano County Transit (SolTrans) currently has a fleet that is 44 percent non-diesel vehicles. SolTrans’ local service fleet consists of four battery-electric buses, two of which are newly deployed, one CNG bus and 21 diesel-hybrids. It has two CNG and 12 unleaded gas paratransit vehicles and its SolanoExpress fleet contains 16 CNG buses with three additional buses set to join the fleet in summer 2020.

“Our preparation for transition began years prior to our first bus purchase,” said Mandi Renshaw, Program Analyst II for SolTrans. “[California] was proposing greenhouse gas emission reductions due to climate change and we knew that we needed to start replacing our diesel commuter buses.”

Renshaw says SolTrans hired a consultant to assist with the development of a long-range plan and the agency created a fuel roadmap to first transition its commuter fleet from diesel to CNG and then to electric buses.

“The hybrids used on the local fleet are not due for replacement until 2023, this allowed us to transition to an all-electric local fleet a few buses at a time,” said Renshaw. “The board approved the roadmap in February 2016 and we started the implementation immediately by constructing a CNG fueling facility.”

Following the completion of the CNG fueling project, SolTrans began researching electrical infrastructure and met several times with its local utility, Pacific Gas & Electric (PG&E). SolTrans signed a contract with PG&E to participate in its Fleet-Ready Program (the program name at the time) in which PG&E will construct, own and maintain all electrical infrastructure from the supply to the customer's meter.

“We commissioned a preliminary study to determine the electrical load required and the estimated cost,” said Renshaw. “We are now in the process of selecting an Engineering Design firm who will interface with PG&E and complete the final design of the charging system to support 60 battery electric buses and 20 electric paratransit buses by 2032.”

While SolTrans describes its transition of its fleet as relatively new, it is developing standard operating procedures including operator training on the new vehicles to optimize performance. Renshaw explains training begins with the bus manufacturer to train the trainers on site on all features and maintenance of the buses. Additionally, SolTrans and its contractor use CAD/AVL systems to monitor all buses, regardless of fuel type, and track route performance measures against SolTrans’ benchmark.

“We are looking forward to building out our real-time performance monitoring capabilities as more electric buses come online and provide us with a more regular data set for daily tracking,” said Renshaw. “Additionally, we have hired a local consulting firm that specializes in electrical usage to monitor our charging system, which entails programming when buses should be charged to ensure they are ready to use when needed but charged at the most cost-efficient time based on our utility rate.”

Renshaw notes that as the agency becomes more familiar with the operational characteristics of battery-electric buses, she expects SolTrans to add key performance indicators, such as energy efficiency by operator per mile/service hour and charging schedule adherence, to measure parameters specific to electric buses.

To accommodate the distances different types of buses can handle, SolTrans has been updating its blocking strategy and building in-route changing opportunities to increase range, which Renshaw anticipates will be revisited annually as the fleet composition changes and the agency begins replacing its local fleet of diesel hybrids with battery-electric buses. One element the fleet transition has not impacted has been the overall spare ratio, but Renshaw says SolTrans is monitoring the real-world operational range of the electric buses to make informed decisions about the bus replacement schedule and the potential need for fleet expansion to maintain service levels. 

Renshaw notes that the decision to purchase two buses early allowed SolTrans a learning opportunity about operating battery-electric buses.

“The amount of research we did to prepare for this transition also made us ready to apply for funding as it became available,” she said.


The Orange County Transportation Authority (OCTA) made news in early February when it debuted 10 new hydrogen fuel-cell electric buses and, what is reported to be, the largest transit-operated hydrogen fueling station in the United States.

“The introduction of hydrogen fuel-cell buses is part of OCTA’s ongoing effort to use the latest in zero-emission transportation technology for a balanced and sustainable transit future,” explained CEO Darrell E. Johnson. “We are proud to be working with all our partners to set a strong example as a large urban transit operator making a positive impact on the environment.”

OCTA retired its diesel-engine buses from service several years ago and in addition to the new hydrogen fuel-cell buses, 500 CNG buses make up OCTA’s 510-vehicle fleet. The authority also expects to introduce battery-electric buses to its fleet in late 2021 and is in the process of procuring 10 plug-in battery-electric vehicles.

While Johnson says OCTA is in the beginning stages of operating a mixed-technology bus fleet, he points to a two-year demonstration project, funded through a state grant, to operate a hydrogen fuel-cell bus as providing ample preparation.

“The demonstration program allowed us to test the technology across Orange County and to learn from how it performed in a variety of conditions and on various routes,” said Johnson. “We learned a great deal from that program and found, over time, that a hydrogen bus could deliver the range and reliability that maintains the high level of service that our bus riders have come to rely on.”

Johnson reports the hydrogen fuel-cell buses can achieve up to 300 miles per day, which meets the demands of OCTA’s fixed-bus routes.

OCTA coach operators are receiving specific training to better understand how the hydrogen fuel-cell buses operate and techniques on throttling and braking that can help achieve maximum efficiency with the new technology. Johnson says all of OCTA’s more than 600 coach operators will be trained to drive the fuel-cell buses, but notes the transition has been smooth due to the similarities between the new fuel-cell buses and current fleet of CNG buses, which were both manufactured by New Flyer.

OCTA has developed a system of metrics and is at the beginning stages of analyzing data, including overall range, miles per kilowatt hour, cost per mile and amount of downtime for maintenance. Johnson expects the type of data collected will evolve over time and will be compared to OCTA’s CNG fleet to ensure peak performance.

“Fortunately, having a hydrogen fuel-cell bus for a two-year demonstration helped work out many of the early questions that we had about operations and reliability before we introduced more fuel-cell buses into our fleet,” said Johnson.

Foothill Transit

Foothill Transit began its transition to electric vehicles in 2010 and currently has a fleet makeup that includes 33 battery-electric buses and 340 CNG buses. Of the 33 battery-electric vehicles, 16 are fast charge buses with the remainder being extended range 440 kilowatt-hour buses.

The current fleet of electric buses is split between Foothill Transit’s two bus yards with the fast charge buses at Pomona and the extended range buses at Arcadia, where the agency recently completed installation of 13 plug-in chargers.

Roland Cordero, director of Maintenance and Vehicle Technology at Foothill Transit, has been involved with the agency’s transition from the beginning and has experienced the evolution of the electric buses.

“The technology is really changing the way we look at the type of vehicles we are able to deploy in terms of providing public transit and in helping develop a sustainable system that will help the communities we serve,” said Cordero.

Foothill Transit will meet the state mandated deadline to transition its fleet to zero-emission by 2040 and hired Burns & McDonnell to develop an electrification roadmap and analysis to incrementally build the infrastructure to support that transition.

Burns & McDonnell completed its report in September 2019, which included evaluations of several variables including bus routes, the number of stops, passenger loads, topography, temperatures and others to determine the energy needs required to operate electric buses.

Felicia Friesema, director of marketing and communications at Foothill Transit, explains the deep dive provided in the report helped with the logistics and planning necessary for charging a larger electric fleet.

“A few buses in the fleet is not that difficult to figure out, but if you’re talking a fleet of over 300 vehicles, that’s a lot of electricity running through your operations facilities,” said Friesema.

While the report provided needed information to plan for a fleet transition, it also shed light on the cost of that transition, which Cordero explains, didn’t just grab his attention, but also the attention of top leadership at Foothill Transit.

“What stood out was the cost of the infrastructure and all the construction related costs to install chargers at our bus yards. It was an eye opener,” said Cordero.

Friesema added, “One of the things that this report from Burns & McDonnell prompted us to do was to look at what our alternatives might be. We're now conducting research, looking into hydrogen fuel-cell vehicles as a possible alternative to the battery-electric buses that would still allow us to meet our zero-emissions requirements. We haven't issued any procurements or made any decisions about that yet, but that research and investigation is ongoing.”

In addition to the report, Foothill Transit has been working closely with its electric power provider, Southern California Edison. Cordero says the power company has been able to help Foothill Transit with the design, installation and construction of grid connections, as well as assisting in the development of electric bus rates through the utility’s Charge Ready Transport Program.

“Partnership with the utility company is very important. I don’t think any transit agency will be able to move forward with a project without getting the utility companies involved,” explained Cordero.

For the electric buses already in service, Foothill Transit utilizes a telematic system from Viriciti to monitor bus and bus operator performance.

“We have an expectation of what the efficiency is supposed to be and monitoring the performance is an important part of operating a battery-electric bus,” said Cordero. “We’re able to monitor in real time how much energy is being used when a bus is being driven, when it’s idling, whether its charging at a charging station, how much energy is being charged back and how many miles of range remains.”

One aspect that Foothill Transit is not looking to change as part of its transition plan is its spare ratio.

“Our approach in terms of taking in new technology is that it should not make our life more complicated,” said Cordero. “Whether it’s a battery-electric bus or a CNG bus, it’s a bus we provide regular service with and there are no additional elements to add, like increasing spare ratio, because that means it doesn’t fit our business model.”

Friesema added that not only should technology not complicate agency operations, but it shouldn’t impact riders either.

“Customers care if they’re getting from Point A to Point B safely and reliably. If we’re deploying an electric fleet and we’re experiencing breakdowns or we’re running out of charge or otherwise not providing the service that they expect, then we’ve failed,” explained Friesema. “I think one of the things we definitely got right with incorporating this interesting and new technology was seamlessly making it part of how we do business in our region.”

In the April/May issue, Part 2: Maintaining the Mix.

About the Author

Mischa Wanek-Libman | Group Editorial Director

Mischa Wanek-Libman serves as editor in chief of Mass Transit magazine and group editorial director of the Infrastructure and Aviation Group at Endeavor Business Media. She is responsible for developing and maintaining the editorial direction of the group and is based in the western suburbs of Chicago.

Wanek-Libman has spent more than 20 years covering transportation issues including construction projects and engineering challenges for various commuter railroads and transit agencies. She has been recognized for editorial excellence through her individual work, as well as for collaborative content. 

She is an active member of the American Public Transportation Association's Marketing and Communications Committee and serves as a Board Observer on the National Railroad Construction and Maintenance Association (NRC) Board of Directors.  

She is a graduate of Drake University, where she earned a Bachelor of Arts degree in Journalism and Mass Communication with a major in magazine journalism and a minor in business management.