Transportation agencies have long been tasked with helping to support community goals of mobility, accessibility, and economic vitality. Recently, there has been a rising interest in having sustainability and livability goals help guide transportation system investments, with considerable focus on the interrelationship between transportation infrastructure, housing, and land use planning. In addition to planning and designing transportation infrastructure, State, regional, and local governments play a key role in operating transportation systems from maintaining local traffic signals and crosswalks to operating regional transit services and Statewide traveler information programs. However, the role that transportation systems management and operations (M&O) plays in supporting livability and sustainability has not been well defined. As a result, transportation planners, operators, and stakeholders are not fully aware of the role that M&O may play in achieving livability and sustainability goals and how M&O strategies can support these goals in a cost-effective and timely manner. This primer describes the role of transportation systems management and operations (M&O) in advancing livability and sustainability. The document highlights the connections between M&O and livability and sustainability objectives and the importance of a balanced, comprehensive approach to M&O in order to support those objectives. The document describes nine key elements for managing and operating transportation systems in ways that support livability and sustainability. The document also provides a vision of how the regional transportation system could look in the future if M&O strategies were comprehensively implemented to advance livability and sustainability goals. Case examples throughout and a section on implementation will help practitioners to get started on implementing M&O to support livability and sustainability in their communities. The primer is directed at transportation planners and transportation system operators at the State, regional, and local levels. It is also meant to support the broader audience of stakeholders involved in all aspects of transportation and community decisionmaking, from elected officials and interested citizens to practitioners in related fields such as land use planning, community development, housing, the environment, and public health.