TTI is providing policy recommendations and evaluating travel behavior for a smartphone-based road user charge system within the Dallas/Fort Worth Region. The project will demonstrate using smartphones to assess toll credits with prices that vary based on location, day-of-week, time-of-day, vehicle classification, vehicle occupancy, air quality, and traffic flow data. No roadside infrastructure or plug-in vehicle devices will be needed as part of the system. The underlying technology for the project is the GoCarma smartphone app, which is already used by more than 50,000 commuters in the region to qualify for high-occupancy vehicle (HOV) toll discounts. The project will assess the impact of various incentives (amounts and form factors) on travel behavior. Participants in the program will receive a credit for participation, but no tolls will be collected for participation. This demonstration is not a direct replacement for the gas tax. Support for the project comes from the Surface Transportation System Funding Alternatives (STSFA) Program.