The Colorado Dept. of Transportation, known primarily as a highway and bridge builder, wants to get into the rail business. CDOT has called for proposals to create a passenger-rail system along Colorado’s Front Range, with trains running from Pueblo in the south through Colorado Springs and Denver north to Fort Collins, near the Wyoming border. More than 85% of the state’s population, nearly 4.9 million people, live within that 173-mile corridor, but state officials expect that number to reach 6.6 million by 2045.