The PRR MP70, also known informally as the "double-deckers", was a class of electric multiple units manufactured by the Pennsylvania Railroad for use on the Long Island Rail Road (LIRR).

The Pennsylvania Railroad manufactured three prototypes in the 1930s and a full fleet of sixty cars in 1947–1949.

A single example, the prototype, is preserved at the Railroad Museum of Long Island.

[8] The cars stood 14+1⁄2 feet 1+1⁄2 inches (4.458 m) tall, short enough for the clearances in Pennsylvania Station and the East River Tunnels.

An early indicator was the LIRR's order in 1953 for twenty single-level multiple units from Pullman-Standard.

[13] The split-level seating slowed boarding at stations and made ticket collection cumbersome.

William Ronan, then chairman of the Metropolitan Transportation Authority (MTA), cited mechanical unreliability, high operating costs, passenger discomfort, and the entry of new M1 railcars into service.

[15] The experience soured the LIRR on the concept, and it did not contemplate double-decker cars again until the late 1980s, when it ordered the C1 coach.