The National Transportation Safety Board issued a series of safety recommendations to the Metro-North Railroad calling for the use of inward and outward facing audio and image recorders and the installation of approach permanent speed restrictions signs along the right-of-ways.

These safety recommendations were developed from information learned during the ongoing investigation into the December 1, 2013 derailment of a Metro-North passenger train in Bronx, New York.

In that crash, the southbound train, consisting of seven passenger cars and one locomotive, derailed on the Metro-North Hudson Line near Spuyten Duyvil Station, killing four and injuring dozens of others.

"The images and audio captured by recorders can be invaluable to our investigators," said NTSB Chairman Deborah A.P. Hersman. "Understanding what is happening inside the cab just prior to a crash can provide crucial information about how to prevent future accidents."

The NTSB has been advocating for inward and outward facing recorders for investigation and oversight purposes since 2007 and has previously made recommendations to the Federal Railroad Administration and other railroads regarding the matter.

Investigators have learned that while Metro-North had posted signs for temporary speed restrictions throughout its rail property, it did not use signage for permanent speed restriction areas, including the area where the accident occurred. Since the accident, Metro-North has installed signage to aid operating crews at four locations with permanent speed restrictions, including the derailment area. However, the NTSB believes that Metro-North should use a more systematic approach and install signage at all locations where permanent speed restrictions are in place, according to a statement.

On Tuesday, Chairman Hersman met with new Metro North Railroad CEO Guillietti to brief him on the NTSB's ongoing investigations and recommendations issued since last May.

The full safety recommendation letter is available at www.ntsb.gov/doclib/recletters/2014/R-14-007-009.pdf