To advance transit asset management, the Federal Transit Administration updated the Transit Asset Management Guide Supplement to provide detailed information about asset category organization and current lifecycle management practices. This Supplement provides a detailed framework for managing assets individually, organized by asset class, as well as a portfolio of assets that comprise an integrated system. This Supplement provides a thorough and detailed understanding of the complexities for managing asset categories, providing stakeholders with a broader understanding of the contemporary practices involved in asset management. This Supplement is organized by the asset classes defined in the TAM Final Rule— Revenue Vehicles, Facilities, Infrastructure, and Equipment. It discusses organizational and maintenance approaches as they relate to these four classes, highlighting the connectivity between individual asset management across classes and how it informs the broader agency asset portfolio.