harness racing
A form of horse racing where the horse pulls a two-wheeled cart called a sulky with a driver.
Harness racing is a type of horse race in which horses compete pulling sulkies.
競馬 is general horse racing, while 繋駕競走 specifically refers to harness racing where the horse pulls a sulky.
Compound of 繋駕 (けいが, 'harness') and 競走 (きょうそう, 'race').