(AP) -- The Obama administration says it's drafting rules to require that railroads install video cameras inside locomotive cabs to record the actions of engineers.

The Federal Railroad Administration also says that other steps aimed at reducing human error are in the works. The cameras have been opposed by labor unions.

Also, the National Transportation Safety Board has sent a letter recommending Amtrak install video cameras in all its locomotive cabs.

Investigators are struggling to determine why an Amtrak train accelerated to twice the speed limit moments before derailing in Philadelphia in May. Their task has been complicated because the engineer says he has no memory of events prior to the crash, and there was no inward-facing camera in the cab.

Amtrak has said it will install the cameras on some trains.