The nation’s freight railroads are going to be able to try relying more on technology and inspect their tracks less often after the federal government approved their waiver request on Friday. The Association of American Railroads trade group asked for the relief from the inspection requirements because railroads believe the automated track inspection technology they use is so good at spotting problems early that human inspections aren’t needed as frequently. The union that represents track inspectors had said that any reduction in human inspections would raise the risk of derailments because there is a long list of things these machines can’t detect.