She has extended a directive to rail companies ordering trains to stick to a 64 km/h speed limit in heavily urbanized areas — a speed limit was brought in last October.
The directive she announced on Thursday also calls for increased inspections along key routes used for transporting dangerous goods.
A government news release says both Canadian National and Canadian Pacific have already imposed a 56 km/h speed limit on their trains.
The Transportation Safety Board included slower train speeds among a list of possible actions the government might consider in a report on rail safety last year, although it did not formally recommend the move.
Rail safety has become a hot-button issue for the federal government since the disaster in Lac Megantic, Que in 2013 in which 47 people died.
A parked train broke loose and derailed in the middle of the Quebec community, setting off a massive fire.
There have been a number of train derailments since that involved hazardous materials.
Last month, the transportation ministers of Ontario and Quebec sent a letter to Raitt expressing concern over the growing number of derailments, calling it unacceptable.