ACMU

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ACMU
ACMU at the North White Plains station in 2004.
In service	1950–2004
Manufacturer	4500 series: St. Louis Car Company 4600/4700 series, MP75: Pullman Standard
Constructed	4500 series: 1950–1951 4600 series: 1962 4700 series: 1962–1965 MP75: 1963
Number built	4500 series: 100 4600 series: 26 4700 series: 61 MP75: 30
Number preserved	4
Successor	4500 Series: M1a 4600/4700 series: M7a MP75: C3
Formation	Single unit
Fleet numbers	NYC: 4500–4599 (later MN 1000–1099) NYC: 4600–4625, 4700–4726, 4750–4783 (later MN 1100–1186) LIRR: 2525–2536, 2675–2692
Capacity	130
Operators	New York Central Penn Central Railroad Conrail Metro-North Long Island Rail Road
Specifications
Car length	85 ft 0 in (25.91 m)
Width	10 ft 11+1⁄2 in (3.340 m)
Doors	2 vestibule doors
Maximum speed	80 mph (130 km/h)
Weight	114,000 lb (52,000 kg)
Traction motors	4 × GE 1240 (100 hp) 4 × WE 1453-A (100 hp) - LIRR MP75 only
Power output	400 hp (300 kW)
HVAC	Electric heat, air conditioning
Electric system(s)	660 V DC third rail
Current collector(s)	Contact shoe
Braking system(s)	Pneumatic
Safety system(s)	emergency brakes
Coupling system	AAR

The ACMUs (short for Air Conditioned Multiple Unit) were a series of electric multiple unit railcars built for the New York Central Railroad in three orders between 1950 and 1965. The ACMUs were intended to replace/supplement the original fleet of heavyweight MU cars, some of which dated to the start of electric operations on the New York Central. These were the first New York Central units to offer air conditioning, with sealed windows replacing the drop sash and clerestory types found on earlier cars. The initial set of 100 cars was retired in 1970, upon completion of the M1 railcar delivery, while the second and third orders, totaling 87 cars, remained in service until 2004, when they were replaced by the new M7 fleet.

An order of near-identical cars was built for the Long Island Rail Road as the MP75 class in 1963. The LIRR cars were eventually converted to non-powered push-pull coaches before being retired in the late 1990s.