The Transit Expressway Revenue Line (TERL), commonly known as Skybus, was a proposed people mover rapid transit system developed by Westinghouse for the city of Pittsburgh, Pennsylvania during the 1960s–1970s. In contrast to the traditional streetcars then in use, the technology used a dedicated elevated concrete track and rubber-tired driverless cars. A demonstrator was built and operated in the South Hills area but political opposition killed the deployment of a larger system.