The Rhode Island Public Transit Authority (RIPTA) is charged with meeting numerous interrelated federal, state, and local requirements for congestion mitigation, air quality improvement, and transit service reliability. Converting its fleet to zero or near-zero emission vehicles has the potential to help RIPTA meet these obligations while supporting various state and local sustainability commitments. However, significant operational, infrastructure and cost constraints exist and must be addressed for long-term success while balancing environmental goals with important co-priorities of affordable service, reliability, equity, and operational flexibility. The introduction of new technologies into the fleet should be done in a manner that minimizes impacts to riders and provides continuity of service while maximizing environmental benefits.
To fully assess the opportunities and implications of fleet conversion and develop a strategy that is sustainable over the long term, a technical assessment of commercially available technologies and their ability to meet RIPTA’s operational needs was conducted. Battery-electric, fuel cell, and natural gas buses were evaluated for commercial readiness, fuel availability, performance, and capital, maintenance, and infrastructure costs. These results informed eight fleet conversion scenarios to one or a combination of alternative technologies and were evaluated against a baseline diesel scenario for cost and emissions over a 30-year timeframe. Although a helpful near-term step, a hybrid-electric vehicle scenario was not included because it did not meet the stated purpose to reach zero or near-zero emissions. These evaluations did not consider incentive programs due the inherent uncertainties of award amounts and timelines, although the report does describe these programs’ potential to improve cost savings.
The analysis shows that while alternative fuel technologies offer higher capital costs and lower operational costs, the operational cost savings do not fully offset incremental costs over time in the absence of incentive funding. Of the alternative fuel scenarios, R/CNG and combination R/CNG+EV offer the most cost-competitive option at $2.61/mi and $2.66/mi, approximately$0.05/mi to$0.10/mi more than the current diesel scenario. All-battery electric scenario costs range from $2.82/mi to $3.33/mi, depending on the particular charging strategies assumed. In terms of emission reduction potential, conversion to 100% electric buses offers the greatest emissions reductions in the long term. Scenarios using natural gas buses fueled with Renewable Natural Gas (R/CNG) offer greater short-term NOx and GHG reductions because the electrical grid is initially powered in part by fossil fuels. Notably, the analysis shows that the additional long-term NOx and GHG emission reductions achieved by electric vehicles over the reductions achieved by R/CNG vehicles are relatively small. Both battery-electric buses and fuel cell buses provided the greatest particulate matter reductions over all timeframes.
Incorporating this research into an action plan requires RIPTA to balance environmental goals with co-priorities of affordable service, reliability, equity, and operational flexibility, all in a context of too few resources to meet current repair and service goals. Over the last few years, there has been considerable excitement from the transport sector on the opportunity to electrify buses. Stakeholders at all levels have focused on the prioritization and uptake of electric vehicles. This provides the opportunity to mitigate the risk of the substantial capital and operational challenges associated with electric buses.
The results of this assessment suggest that RIPTA should adopt a graduated program that leverages equipment demonstrations to provide additional experience with zero-emission buses in RIPTA’s operations while working toward a long-term transition to a fully zero-emission fleet. Additionally, RIPTA should initiate regular engagement with local utilities and state agencies to address infrastructure upgrades and financing needs as discovered through these processes.
Specifically, RIPTA proposes the following near-term steps over the next three years.
- Develop a zero-emission pilot program to demonstrate commercially available electric transit buses on a short-term basis in RIPTA’s operations
- Leverage available incentive funds at the state and federal level to subsidize the costs of the pilot program
- Develop an Electric Bus procurement specification
- Reassess the costs and challenges of zero-emission technologies over the course of the pilot program and update this Sustainable Fleet Transition Plan based on those reassessments
- Monitor R/CNG opportunities in the medium term in the event that zero-emissions battery-electric bus technology proves insufficient to address statewide transit needs or is too costly.
- Continue to work with state agencies and the local utility to:
- Plan for a larger scale transition to zero-emissions that will likely require substantial electrical infrastructure upgrades and investments
- Develop policies to clarify rules, roles, and responsibilities for electricity use and management
- Evaluate options to monetize these infrastructure investments through other mechanisms (energy/demand services, grid resiliency, etc.)