Companies sending oil from the Bakken shale reserve area by rail are reminded of their responsibility to give advance traffic notices, a federal regulator said.

"Transparency is a critical piece of the federal government's comprehensive approach to safety," U.S. Transportation Secretary Anthony Foxx said in a statement. "The department is committed to making certain that states and local officials have the information they need to prepare for and respond to incidents involving hazardous materials, including crude oil."

The department's Federal Railroad Administration sent notification to railroads reminding them of their obligation to notify state and tribal governments in advance of shipments of Bakken crude oil by rail. Since May 2014, companies delivering more than 35 tankers of Bakken crude oil, or about 23,800 barrels, by rail are required to give such notification.

The Department of Transportation last year issued a safety alert saying the type of crude oil in the Bakken reserve area of North Dakota may be more flammable than other grades. The North Dakota Petroleum Council followed with its own study saying crude oil taken from the Bakken shale does not pose a greater risk when transported by rail.

North American crude oil production has increased to the point that there's not enough pipeline infrastructure to handle deliveries. That leaves energy companies to rely more on rail as an alternate transit method and, with that, comes more derailments involving trains carrying oil.

Federal rules extend beyond the shipment notification to include the eventual elimination of railcars designated DOT-111, a model involved in a string of sometimes fatal derailments involving crude oil shipments.

The American Fuel & Petrochemical Manufacturers group sent a letter to the federal government calling for what it said was a holistic approach to oil-train safety. The AFPM points to industry data that says that, on average, three derailments per day occur not because of car design, but because of poor track integrity and human error.

Earlier this year, federal government called for advanced braking systems on rail cars in an effort to decrease stopping distance and keep more rail cars on the track should a derailment occur.

"The Federal Railroad Administration will continue with random spot checks and regular compliance audits to ensure that states, local communities, and first responders have the information necessary to respond to a possible accident," added acting FRA Administrator Sarah Feinberg.