What should one do when truck brakes fail while it is moving fast down a steep slope?

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There is this horrific accident I witnessed that has failed to leave my memory for close to a year now. It happened in Nairobi – our capital where I used to live and work as an assistant graphic designer before I retreated to the village and began concentrating on farming. I was walking to my rented apartment having shortly alighted from a bus I had boarded from town. Suddenly there was a loud hooting and upon looking, saw a very fast-moving truck laden with many bags of cement. It was moving downslope and had all its headlamps on and brightest. Luckily, vehicles in front of it gave way and non was hit. The truck however, upon reaching a speed bump downslope, overturned badly, crashing into a perimeter wall of a nearby eatery. The cabin was completely destroyed and all of the two occupants died on the spot. It was a horrific scene. I overheard some people present saying that it was another case of break failure due to insufficient pressure in the system tanks. I was left wondering what one should do to stay alive in case truck breaks fail while moving in high speed down