The evolution towards mass-produced automatic transmissions continued with the 1933-1935 REO Motor Car Company "Self-Shifter" semi-automatic transmission, which automatically shifted between two forward gears in the "Forward" mode (or between two shorter gear ratios in the "Emergency low" mode). Driver involvement was still required during normal driving, since standing starts required the driver to use the clutch pedal. This was followed in 1937 by the Oldsmobile "Automatic Safety Transmission". Similar in operation to the REO "Self-Shifter", the "Automatic Safety Transmission" shifted automatically between the two gear ratios available in the "Low" and "High" ranges and the clutch pedal was required for standing starts. It used a planetary gearset. The Chrysler "Fluid Drive", introduced in 1939, was an optional addition to manual transmissions where a fluid coupling (similar to a torque-convertor, but without the torque multiplication) was added, to avoid the need to operate a manual clutch.