Obama’s executive order tells workers not to text while driving federal vehicles, using government-supplied communications devices or in private vehicles on official business, the administration said in an executive order announced today.

“This order sends a very clear signal to the American public that distracted driving is dangerous and unacceptable,” Transportation Secretary Ray LaHood said at a two-day conference on the issue that ended in Washington today. “It shows that the federal government is leading by example.”

The ban applies to the 2 million employees counted by the Office of Personnel Management and the more than 700,000 U.S. Postal Service employees.

The move follows the Transportation Department’s statement yesterday that about 16 percent of fatal crashes last year involved a driver whose attention was interrupted in some way, compared with 11 percent in 2005.

The agency said it will make permanent restrictions on use of mobile phones and other electronic devices for train operators. The Federal Railroad Administration announced a ban after last year’s collision between a Los Angeles Metrolink commuter train and a Union Pacific Corp. locomotive. Evidence showed crew members were sending text messages before the crash.

The Transportation Department also plans to ban texting by commercial-truck and interstate-bus drivers, to restrict their mobile-phone use and to revoke commercial licenses of school-bus drivers convicted of violating texting rules, LaHood said.

The rules would apply to computers installed in trucks that commercial drivers use to plan routes and communicate with their employers, LaHood told reporters.