WASHINGTON — In the wake of a deadly train accident in Canada, the U.S. Federal Railroad Administration has issued a series of measures to be undertaken by all railroads to help prevent trains operating on mainline tracks or sidings from moving unintentionally.

The half-dozen measures in the emergency order take particular aim at trains that move hazardous materials such as crude oil and ethanol. All railroads must undertake the measures within the next 30 days, the FRA said in a statement Friday night.

On July 6, a parked Montreal, Maine & Atlantic Railway train with 72 tankers of crude oil rolled down an incline, derailed and crashed in downtown Lac-Megantic, Quebec. Several tankers exploded, destroying 40 buildings in the lakeside town of 6,000 and killing 47 people.

Only one person had been assigned to the nearly mile-long train, which had been parked overnight. After the wreck, Canadian transportation authorities banned one-man crews for trains carrying dangerous cargo and said such trains will not be allowed to be left unattended on a main track.

The FRA's emergency order didn't ban one-man crews but the Transportation Department, which oversees the FRA, said in the statement that "railroad safety is enhanced through the use of multiple crew members." In a separate safety advisory, the Transportation Department recommended that railroads review their crew staffing requirements for transporting hazardous material and ensure that they are adequate.

Under one of the FRA orders announced Friday, no train or vehicles transporting specified hazardous materials can be left unattended on a mainline track or side track outside a yard or terminal, unless specifically authorized.

Another order mandates that, in order to receive authorization to leave a train unattended, railroads must develop and submit to the FRA a process for securing unattended trains transporting hazardous materials. Included in the order are locking the locomotive or otherwise disabling it, and reporting among employees to ensure the correct number of hand brakes are applied.

"Today's action builds upon a comprehensive regulatory framework we have had in place for some time," FRA Administrator Joseph C. Szabo said in a statement. "The safe shipment of all cargo is paramount and protecting the safety of the American public is fundamental to our enforcement strategy and we are encouraged by the industry's willingness to cooperate with this approach going forward."

The FRA said it will convene an emergency meeting of its Railroad Safety Advisory Committee to consider what additional safety measures may be required as it continues to evaluate safety procedures following the crash in Quebec.

"Safety is our top priority," Transportation Secretary Anthony Foxx said in the statement. "While we wait for the full investigation to conclude, the department is taking steps today to help prevent a similar incident from occurring in the United States."