General Motors Co. said Thursday it’s nearly doubling the mileage of roads that can be used with its Super Cruise advanced driver assistance system. The expansion from 400,000 to 750,000 miles adds more remote highway options, GM said. The new roads have started being added incrementally over-the-air, at no additional charge to customers. They will continue to be added through 2025. The Cadillac CT6, Chevrolet Bolt EUV and Cadillac XT6 will not receive the expansion because they are built on an older electrical system.