The Jake Brake: The Breakthrough That Saved Trucking

Every driver heading down a long mountain grade knows this feeling. The truck starts rolling faster than it should. You tap the brakes once, then again, but the truck keeps picking up speed. And somewhere on that descent, you feel something no amount of experience fully prepares you for. The pedal isn't doing what it's supposed to do. The drums are hot. The truck is still accelerating. And the bottom of the mountain is still a long way down. This is the story of how one man's near-death experience on a California mountain pass gave truck drivers something they had never had before, a way to fight gravity with the engine itself. Early heavy trucks relied entirely on friction brakes to control their speed. Press the pedal, brake shoes press against a drum, and the truck slows as the brakes turn motion into heat. On flat ground or gentle grades, it worked well enough. But on a long sustained downhill run, the brakes were absorbing enormous amounts of energy, and all of that energy went into heat. As the drums climbed past 500° and kept rising, the friction material would progressively lose its grip in a phenomenon known as brake fade. It didn't announce itself suddenly. It crept in gradually as the temperature built. And by the time a driver recognized what was happening, the truck that weighed tens of thousands of pounds and was pointed downhill had very little ability to slow down. The runaway truck was not a rare or theoretical event in the early decades of commercial trucking. It was a recognized occupational hazard, something drivers talked about and planned around and feared. Studies from the late 70s and early 80s documented thousands of runaway truck incidents each year. As the interstate highway system allowed trucks to travel faster over longer mountain grades, states began building dedicated runaway ramps as a last resort safety measure. with more than 150 constructed by 1990. Those ramps were not a precaution. They were an acknowledgement that brake failure on steep grades was a predictable, recurring problem that the industry had not yet solved. The problem grew worse as trucks grew heavier. The diesel engine changed everything about what a commercial truck could haul.