Oldslowchevy is right about air brakes having way to many safety backups for something like this to happen by random chance. If they loose air pressure they lock up. If the service line comes off the trailer, you still have tractor brakes. Not near as effective, but you still have brakes. If the emergency line comes off the trailer, the trailer brakes lock up.
What gets drivers in trouble, is using the brakes too much all at once, overheating them. Only two things could cause that truck to run away down that off ramp. Brake fade, the brakes get overheated and stop working, or the valve under the brake pedal failed. Most trucks have a separate valve that will run just the trailer brakes, a bar next to the steering wheel you pull down.
I have either wrenched on or driven trucks for 15 years and have never seen a brake pedal valve fail.
Am I saying I know what happened here by watching a video? No. But I can apply my experience to what I see. As will most other drivers who see this video. The guy deserves all the credit in the world for not slamming into those cars at the stop sign. It does say that he hit one in the report, but it looks like he whipped the trailer into it.
But from my perspective, the first thing I thought when I saw that video, is why is this guy going so fast down the ramp? He should have been using his engine brake to slow the truck before he exited the freeway.
Never trust that your brakes will always work. Never. They are the most important safety item on any vehicle. Air brakes need to be checked and adjusted DAILY. Failure to do this can kill someone. I pull doubles at 129,000 lbs. Brakes are my best friend and biggest pain in my ass. I have 20 of them on my rig and they require alot of my time. But ask any driver who has ever had a brake fade incident, you start kissing your ass goodbye till you get stopped. Then you call your wife and tell her how much you love her and the kids, because you just cheated death. That's how it feels.
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