Gravity racer
（重定向自Billy cart）
![Children racing in a soapbox](/Images/godic/202412/24/Soapbox_racers1628.jpg")
![Soapbox cars at the finish line of a race](/Images/godic/202412/24/SoapBoxRaceFinishLine1628.jpg")
![An official Soapbox derby racer from 1967](/Images/godic/202412/24/Soap_Box_Derby_Racer1628.jpg")
![Gravity race in Montreal, 1948](/Images/godic/202412/24/Feature._Coaster_Classic_BAnQ_P48S1P166031628.jpg")
A gravity racer or soapbox is a motorless vehicle which is raced on a downhill road either against the clock or against another competitor. Although most are built for the purpose of recreation, some gravity racing teams take the sport more seriously and compete to win. They are propelled by gravity and can achieve speeds upwards of 112 km/h (70 miles per hour).