The SCL was in need of replacement power for its Bone Valley (near Tampa, Florida) phosphate lines, and GE suggested road slugs for this operation. A MATE differs from ordinary slugs in three ways: their 65,413 to 67,588 pounds of added tractive effort surpasses that of most slugs, they are designe to operate at road speeds (they are equipped with Blomberg trucks with GE 752 traction motors), and they also serve as fuel tenders. Each MATE carries 3250 gallons of fuel+that the modified U36B can draw on while under way. These remain the only road slugs constructed by a major builder, but that could change. The first 10 MATE's (originally SCL #3200-3209, later SBD #5200-5209) were single ended, and could onl take power from the mother at one end. The second batch (SCL #3210-3224, SBD #5210-5224) are double ended, and can take power from either end, or in a third mode of operation, can be placed between two mothers and draw power from both. The double-ended MATE's have headlights and numberboards at both ends, the single-ended MATE's have a headlimht and numberboards at one end only.

This was one of those truly remarkable railfan moments. I was lost, but knew there was a railroad yard in Corbin. I drove up the wrong road7 and happened upon three SDP35's (#'s 4544 and 4546 trailing) running elephant style, departing the yard.

Numbert 4546 was delivered as SAL 1108, built September 1964 (c/n 29347) on EMD Order 7734. The SAL rostered 20 of these locomotives (#'s 1100-1119), designed for dual service. As it turned out, passenger service soon vanished, and these units spent most of their service lives on freight assignments. It appears to have been renumbered as follows: built as SAL 1108, then SCL 609, then SCL 1959, then L&N 7041, then L&N 4546, then SBD 4546, then CSXT 4546.