Regulators are taking another step in ensuring the safe transport of crude oil by rail by mandating better brake monitoring, the transport secretary said.

The Federal Railroad Administration issued a ruling requiring railroad employees to get secondary confirmation that equipment meant to secure trains and equipment are deployed properly. Transportation Secretary Anthony Foxx said the mandate is part of a comprehensive effort to improve the safe transport of crude oil by rail.

"Verifying that a train has been properly secured is a common sense solution to prevent accidents," he said in a statement.

More than 40 people were killed in Lac-Megantic, Quebec, in 2013 after the derailment of a train carrying tankers of crude oil from North Dakota to Canadian refineries. Montreal, Maine and Atlantic Railway, the train's operator, blamed the air brakes on the locomotive holding the freight for the incident

The U.S. ruling requires an employee to get verification from a second worker that the train is properly secured and applies to unattended trains carrying more than 20 cars of high-hazard flammable liquids.

U.S. regulators in early 2013 started an operation dubbed Bakken Blitz to examine how shippers are classifying crude oils that may be more prone to detonate in some types of rail tankers. Bakken oil, a grade found in North Dakota, was found to be potentially more flammable than other types of oil, though industry supporters questioned those findings.

North American crude oil production has increased to the point that it's more than the existing pipeline infrastructure can handle, leaving energy companies to rely more on rail for transport. More rail disasters involving crude oil have occurred in recent years as a result.

"While today's rule came out of a lesson learned from the Lac-Mégantic derailment, FRA will not hesitate to take additional actions to keep the rail system in the United States safe," acting FRA Administrator Sarah Feinberg said.

The Canadian government rolled out new regulations in April 2014 aimed at increasing safety on the nation's rail system. The measure from regulator Transport Canada started with an order to remove around 5,000 tanker cars designated DOT-111, the type involved in the Lac-Megantic incident, from service almost immediately.