There's a difference between an end of train device and a marker or FRED. A marker is just a simple thing to distinguish the end of a train (a flag, lantern, or flashing light typically). An end of train device also incorporates a flashing light to indicate the rear of the train, but it also communicates with the head end of the train, relaying the brake pipe pressure reading on the rear of the train to the front of the train. Class 1 railroads tend to use the EOTD, as well as some short lines that handle long trains. On the LIRR (and NYAR), the trains aren't usually all that long, so it doesn't take all that long for a crew member to walk to the back of the train to read the gauge to check the pressure on the rear.