WASHINGTON — The Federal Railroad Administration issued two rules Friday aimed at preventing injury to track workers, an outgrowth of accidents including the death of Metro-North supervisor Robert Luden, who was killed in 2013 by a New York-bound commuter train. The first rule, governing warnings that crews are on tracks, essentially is a belt-and-suspenders series of redundancies aimed at making extra sure trains don’t barrel through mistakenly while work is in progress. In the wake of the 2013 fatality, Metro-North started its enhanced employee protection system,’’ in which the dispatch system locks up a portion of track.