Also, fail-safe only works so far. A parked car needs to have handbrakes set or wheels chocked, since the air can eventually bleed out of the reservoir and rele

Also, fail-safe only works so far. A parked car needs to have handbrakes set or wheels chocked, since the air can eventually bleed out of the reservoir and release the brakes. The Lac-Mégantic disaster [0] involved insufficient handbrakes set on a train parked on a grade. [0] https://en.wikipedia.org/wiki/Lac-M%C3%A9gantic_rail_disaster https://en.wikipedia.org/wiki/Lac-M%C3%A9gantic_rail_disaste...