When brake pedal is pushed by the driver, brake fluid is forced into the brake cylinder by the action at the master cylinder, and the two pistons are forced outward.

当驾驶员踩下制动踏板时，制动液由于主缸的作用进入轮缸，推动两个活塞向外侧移动。

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The cause of the crash is not yet clear, but California Highway Patrol spokesman Mario Lopez was quoted by the Associated Press as saying that the bus driver reported brake problems as he descended a road leading from the Big Bear ski resort area.

BBC: California bus crash kills eight and injures dozens

He said he didn't notice whether the driver tried to brake before hitting the other train.

CNN: Investigator: D.C. Metro crash 'a scene of real devastation'

In motor racing, you can see how fast a car is going, whether the driver is using the brake or the throttle and a host of other data.

ECONOMIST: Sport and the media are natural bedfellows