Recently over 5 years of field observations were concluded of the value-priced express lanes that opened December 27, 1995, in the median of State Route 91, in Orange County, California. Data collection, covering about a year and a half of observations to establish baseline conditions before opening day, included traffic measurements, vehicle occupancy counts, transit ridership, and comprehensive travel surveys of current and former commuters. The corresponding data analysis included the calibration of choice models of route, occupancy, transponder acquisition, and time-of-day behavior of commuters and the estimation of air pollution emissions. Findings are presented on traffic trends, toll lane use, travelers' responses to changing congestion and tolls, shifts in ridesharing and transit use, shifts in trip purpose, differences associated with income and other demographics, public opinion, collision experience, and the results of choice and emissions modeling. As the first practical application of value pricing in the United States, the State Route 91 express lanes provide many important insights, both technical and institutional, some of which are relevant to the implementation of value-pricing projects in other locations.