RS-1
Built between 1941 and 1960, the RS-1 had the longest production run of any diesel locomotive in North America and its carbody became the standard for later road switchers.
RS-2
Conrail inherited four RS-2's from Lehigh Valley and 14 from Erie Lackawanna, assigning them to series CR 5200-5217.
RS-3
Conrail inherited RS-3's from Erie Lackawanna, Penn Central, Jersey Central, and Lehigh Valley. The units were assigned various series.
RS-3M
Penn Central and then Conrail began rebuilding aging ALCo RS-3's, replacing the prime movers with ones from EMD. They occupied series CR 9903-9999.
RS-11
Conrail inherited their RS-11's from Lehigh Valley (LV 400-403) and Penn Central, giving them series CR 7587-7654. CR 7592, 7598, 7599 were scrapped at Precision late 1977 or early 1978.
RS-27
Conrail inherited their small fleet of RS-27's from Penn Central, placing them in series CR 2400-2414. They look like a cross between a Century class and an RS class locomotive.
RS-32
Conrail inherited their RS-32's from Penn Central (NYC), placing them in series 2021-2044. By 1979 only 6 units were still on active roster. A few years later, all were gone.
RSD-5
Conrail inherited only a handful of these oddball locomotives and quickly retired them within a few years.
RSD-15
Conrail either converted their RSD-15's into MT-6 slugs between 1978 and 1979 or scrapped them early on because they were unreliable, oddball locomotives.
S-2
Conrail inherited their S-2's from Penn Central and Erie Lackawanna. They were in series 9633-9660 as well as several non-consecutive series in the 9700's and 9800's.
S-4
Built between 1950 and 1961, ALCo's S-4 differs from the S-2 only in the trucks, with the S-2 using ALCo's own Blunt trucks and the S-4 using standard AAR type A switcher trucks.
T-6
Conrail inherited six of these locomotives from the Penn Central, who inherited them from the Pennsylvania Railroad.