CHAPTER 1
Introduction

The guide provides an overview of resilience and ZEB fleet transition planning in transit, specific threats impacted by, and adaptation measures relevant to zero-emission (ZE) fleets, and a framework for updating resilience plans for ZE fleets. The guide also contains sample scenarios for evaluating threats to ZE bus (ZEB) fleets and case studies of American transit agencies that have conducted planning efforts or implemented adaptation measures to mitigate risks associated with ZE transit bus fleets.

Scope

Resilience is a broad concept with many definitions, and establishing a common terminology is critical to a productive conversation. Resilience is often used in the context of climate adaptation to refer specifically to an assetʼs vulnerability and/or response to extreme weather events and natural hazards. This guide will cover natural hazards such as extreme heat and sea level rise, but also energy system failures, cybersecurity breaches, and market instability (U.S. DOT 2021a). Based on a literature review and transportation stakeholder interviews, Weilant, Strong, and Miller (2019) defined resilience in transportation as “the ability to adapt to, recover from, respond to, and bounce back quickly” from threats. In this guide, transit agencies are defined as resilient when they can meet level of service needs when faced with adverse conditions. The scope of these guidelines focuses on operational resilience and maintaining defined service levels in both day-to-day operations and during emergency events.

Motivation

Resilience planning within public transit is important for ensuring that the needs of communities, especially those that are most vulnerable, continue to be met when adverse events occur. The extreme conditions that come with these adverse events then negatively impact the energy systems and infrastructure that a transit agency depends upon in its transition to ZEB fleets (U.S. DOT 2021a). Transit agencies recognize their importance in serving communities, and establishing resilience plans is a necessary step to providing a critical level of service, despite adverse conditions.

While there are many existing guidelines for resilience in a transit or transportation context from the FTA, TCRP, and the American Public Transportation Association (APTA), none specifically address the unique risks and adaptations for ZE fleets and systems, and thus, provide a starting point but not a complete picture for an agency with ZE vehicles in its fleet. Additionally, the ZE fleet transition in the United States is growing quickly, in large part motivated by a need to improve public health, among other things, and increasingly dictated by state and local mandates

and policies such as Californiaʼs Innovative Clean Transit and Massachusettsʼs Zero-Emission Transit Bus Acquisition Requirement (California Air Resources Board 2018, U.S. Department of Energy 2022a). Because most agencies (60%) in the United States currently have ten or fewer ZEBs, they have not had to modify their resilience plans or implement any new adaptation measures to address threats and consequences specific to ZEBs; however, this will not be sufficient as agencies increase the percentage of their fleets powered by alternative infrastructure-dependent ZE technologies (Hynes et al. 2024).

Many transit agencies have prepared ZE transition plans. The state of California has required them under their Innovative Clean Transit regulation, and FTAʼs Low or No Emission Vehicle Program requires a ZE transition plan (California Air Resources Board 2018, FTA 2022). However, very few of these transition plans focus on resilience, and as a result, agencies have many questions about how to incorporate resilience into their ZEB fleet planning. This guide aims to provide a framework for leveraging existing resilience and ZEB transition plans to develop a comprehensive resilience planning document for ZEB fleets.

For the complete literature review, see Appendix B.