The federal safety agency that investigates transportation accidents is banning text-messaging and talking on cell phones by its employees while driving on government business. National Transportation Safety Board’s 400 employees will no longer be able to text or talk on cell phones while driving during work hours nor while driving during off-hours if they’re using a government-issued wireless device. The board’s chairwoman, Deborah Hersman said she’s adopting the policy because she wants her agency to follow the safety practices it recommends.