"A Transportation Research Board (TRB) conference on U.S. and international approaches to performance measurement for transportation systems was conducted May 18 through 20, 2011, at the Arnold and Mabel Beckman Center of the National Academies in Irvine, California. The theme for the fourth in a series of international conferences, driving change and being driven by change, captured the changing environment in which transportation services are delivered as well as the role of performance measurement in delivering these services. TRB assembled a committee appointed by the National Research Council (NRC) to organize and develop the conference program, which included five tracks: Driving forces for change; Performance-based decision making: the bucks start here; Data collection and analysis technologies; Drivers and applications; and Capturing system performance: new measures for difficult-to-measure topics. Each track consisted of a plenary session followed by three concurrent breakout sessions. These proceedings follow the conference format, with the plenary sessions and the breakout sessions for each of the five tracks presented in chronological order. The breakout sessions and the closing session gave participants the opportunity to provide ideas and suggestions on further research, technology transfer, and training. Research topics identified for potential consideration are listed in the section on concluding remarks. The conference also featured an interactive poster session. Summaries provided by the poster authors are presented in Appendix A. The conference attracted 130 participants from Canada, Germany, Japan, the Netherlands, South Africa, and the United States, and featured transportation specialists who offered real-world expertise on the application of performance metrics and case studies. This range of experiences provided attendees with a comprehensive overview of the techniques and approaches being applied to transportation systems both in the United States and abroad. The speakers reflected on the significant evolution of performance measures since the first conference was held in 2000 as well as the increase in their use throughout the transportation industry. As a key tool for delivering results and establishing accountability for transportation systems worldwide, performance measurement is being applied to gauge and evaluate a wide range of transportation activities, from the efficacy of transit operations and congestion management to organizational excellence, program budgeting, and customer satisfaction. The Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU), the previous federal surface transportation spending bill, expired on September 30, 2009.