A spate of train collisions in 2011 -- some of which resulted in fatalities -- have prompted the National Transportation Safety Board (NTSB) to warn the industry to obey speed limits.

Recommendations on the topic issued to government, industry and labor unions focus on the need for railroads to inform their employees about the accidents and to emphasize adherence to speed regulations.

The five freight train rear-end collisions last year all involved crewmembers failing to operate their trains at the required stricted speed, according to the NTSB:

• Red Oak, Iowa, April 17, 2011, BNSF
• Low Moor, Virginia, May 21, 2011, CSX
• Mineral Springs, North Carolina, May 24, 2011, CSX
• DeWitt, New York, July 6, 2011, CSX
• DeKalb, Indiana, August 19, 2011, Norfolk Southern

The accidents in Red Oak and Mineral Springs resulted in crewmember fatalities and are still under investigation by the NTSB. Four of the five accidents occurred on railroad lines over which Amtrak passenger trains operate.

"Because these accidents occurred on different railroads and under different circumstances, the NTSB is concerned that noncompliance with restricted speed requirements may be an issue affecting a broad segment of the U.S. railroad industry," the Board said in a statement.

Recommendations were issued to the Association of American Railroads, the American Short Line and Regional Railroad Association, the Brotherhood of Locomotive Engineers and Trainmen, and the United Transportation Union.

"Signal systems provide for the safe separation between trains. However, there are times when trains are authorized to occupy the same sections of track. In these cases, safe train operations rely solely on crewmember compliance with the railroad's restricted speed requirements.

"Typically, these requirements include 'being prepared to stop within one-half the range of vision.' Complete understanding of and strict compliance with restricted speed requirements are absolutely mandatory to prevent catastrophic train collisions.

The safety recommendation letters can be viewed at: www.ntsb.gov/safety/safety_recs.html