The Federal Transit Administration "is opening the door to an evaluation that is more subjective than it has been in the past and more prone to forecasting error," said Horner, a former chief counsel to the agency during the Bush administration.
The public will have 60 days to comment on the proposed regulations before the transit agency writes final rules.
"By focusing on broad social benefits and broad environmental benefits, this administration is fixing a misstep of the previous administration in a way that's going to be helpful to transit riders, transit agencies and the environment," Deron Lovaas, transportation policy director for the Natural Resources Defense Council, a New York-based environmental advocacy group, said in a phone interview.