dead man’s pedal
n.— «Hardly noticeable, under his right foot, is a small pedal—resembling the clutch pedal on your automobile. “That’s called ’dead man’s pedal’,” Charlie explains. “The weight of my foot holds it down. If for any reason my foot should be removed—in case of heart failure or if I should be thrown from the seat—the motors would be switched off and the brakes locked.”» —“High For Streamliners” by Andy Hamilton Los Angeles Times Sunday Magazine June 20, 1937. (source: Double-Tongued Dictionary)