Once a rarely used emergency brake, the sidecar mechanism has become a recurring feature of Korea's stock market amid bouts of extreme volatility. Its growing use has raised questions about its effectiveness, as stocks have often continued to plunge until circuit breakers were triggered, industry officials said Thursday. According to the Korea Exchange, sidecars have been triggered 43 times in the benchmark KOSPI this year, far surpassing the 26 activations recorded during the 2008 global financial crisis. They have also been triggered 29 times on the secondary Kosdaq, bringing the total number of sidecar activations in Korea’s stock markets this year to 72. Introduced in 1996, the sidecar is designed to prevent sharp price swings in the futures market from spilling over into the spot market through program trading. On KOSPI, a sidecar is triggered when KOSPI 200 futures move by at least 5 percent and remain at or beyond that threshold for one minute. On Kosdaq, it is activated when Kosdaq 150 futures move by at least 6 percent and the spot index moves by at least 3 percent in the same