Facilities Management Systems: Volume 4, Support Services, Infrastructure & Sustainability expands the facilities management framework beyond maintenance and physical asset care into the broader operational systems that sustain and support the built environment. This volume examines the structured management of custodial and environmental services, utility and central plant operations, transportation systems, multi-site resource coordination, sustainability initiatives, resource conservation, and environmental stewardship. Each chapter presents these functions as governed systems within the broader facilities management framework, emphasizing leadership, operational control, performance measurement, and long-term organizational alignment. Designed for facilities leaders, operations professionals, engineers, and infrastructure managers, this volume provides practical guidance for structuring and governing the support systems that enable facilities organizations to operate efficiently, reliably, and sustainably at scale. As part of the Facilities Management Systems series, Volume 4 builds upon prior volumes by extending facilities leadership into the operational support, infrastructure, and stewardship systems required for modern facilities management excellence.