Caisse à savon is a gravity racer cart also called soft box vehicle. It is a vehicle without an engine that moves by the force of gravity alone which they raced on a downhill road either against the clock or against another competitor. This motorless vehicle was originated in United States in 1933 then takes off worldwide. In France, the first motor Derby under 15 was organised in 1950, where in they were forced to build their soft boxes with their own hands. Today races are organised by committees throughout the country.
In Montauban, south west of France this traditional sport held last Sunday, April 7, 2019. Several categories were proposed; for kids, adult single and adult doubles.