The pendulum car was an experimental tilting coach built by the Pacific Railway Equipment Company (PERC) in the early 1940s. It used an innovative coiled spring suspension system that allowed the cars to lean into curves, thus increasing passenger comfort during high speed travel. PERC built three cars which were tested on American railroads throughout the 1940s, but the advent of World War II, and their high cost relative to conventional equipment, prevented their wider adoption.