OMAHA, Neb. (AP) — The nation’s largest railroad union wants federal regulators to do more to ensure conductors are properly trained in the wake of two recent trainee deaths.

The Transportation Division of the International Association of Sheet Metal, Air, Rail and Transportation Workers union that represents conductors wants the Federal Railroad Administration to establish clear standards for how long new employees are trained and who mentors them to teach them the craft after they finish their formal training.

The union said the recent deaths of two CSX trainees on different occasions in Maryland over the past two months highlight the need for better training. The FRA did put out a safety advisory earlier this month about conductor training after the latest death, but the union wants regulators to take firm action. Earlier this year, a third conductor — this time one with 18 years experience on Norfolk Southern — was killed in an accident at a steel plant in Ohio.

FRA officials didn’t immediately respond to the union’s statement Wednesday, but the head of the agency sent a letter to all the CEOs of the major freight railroads earlier this week expressing similar concerns. Administrator Amit Bose is urging the railroads to improve their training but the agency isn’t requiring changes with formal rules.

“FRA believes that correcting the underlying deficiencies in railroads’ training, qualification and operational testing programs is critical to reducing the risk associated with the conduct of certain tasks,” Bose wrote.

In the most recent death, Travis Bradley died Aug. 6 after he was crushed between the train he was riding on the side of several parked locomotives. Earlier this summer, Derek Scott “D.S.” Little died in late June after he fell off a railcar and was struck by a train. Both deaths happened in railyards.

Railroad safety has been a key focus this year ever since a Norfolk Southern train derailed near the Ohio-Pennsylvania border on Feb. 3. Thousands of people had to evacuate their homes after authorities released hazardous chemicals and set fire to them to keep five tank cars from exploding.

Congress and regulators called for reforms after that derailment and railroads announced some plans to improve safety. But little has changed in the industry and a bill requiring railroads to make changes has stalled in the Senate.

The SMART-TD union said the trainings issues are especially important now because the major freight railroads have been hiring new conductors as quick as possible and rushing them out to work on the rails. And generally there is little training for the experienced conductors who serve as mentors.

“In a work environment as dangerous as our country’s railroads have proven to be historically, it is unthinkable that there is not a program in place to train the trainers. It is in most scenarios still the luck of the draw,” the union said.

CSX and Norfolk Southern both announced agreements with SMART-TD last month to enhance conductor training. CSX said it planned to extend its classroom training by a week to five weeks while Norfolk Southern announced a more comprehensive list of reforms.

A CSX spokesperson said the safety of the railroad’s workers is a priority, and CSX responded to the recent deaths with intensive training about safety rules and the hazards of riding on trains as well as extending training for new hires.

“CSX continues to mourn the loss of Travis and Derek, and our thoughts are with their family and loved ones. At CSX, our goal is zero accidents and injuries, and we remain vigilant in working toward that effort,” the spokesperson said.

Norfolk Southern didn’t immediately respond to the union’s concerns Wednesday, but when it announced its training changes CEO Alan Shaw said the moves were meant to “make sure our newest employees — our conductor trainees — have the skills and knowledge to get the job done as safely as possible.”