The following is a true story. The names have been changed and locations omitted, as the driver is awaiting trial for vehicular homicide.
Joe Doakes is cruising along a winding, hilly two-lane state highway in his company-owned 18-wheeler. It's a route often used by truckers to reach customers in this largely rural area. It's late in the afternoon on a fall day. It's rained lightly off and on all day.
Joe's tractor is less than 6 months old. It's got lots of power and it's fast. He's pulling a 2-year-old, 53-foot van. His freight's been delivered, except for a couple of pallets in the nose of the trailer. He has only 30 miles to go and figures he can still deliver, so he's steaming along at a good clip even though the posted speed limit is 55 and he isn't familiar with this highway.
Though there are hills, Joe doesn't need to downshift. As darkness begins to fall, it starts to rain lightly again. The road is black asphalt and gets slick when it's rainy. There are no streetlights, just the reflection of headlights from oncoming cars.

Joe's in top gear (of his nine-speed transmission) and the rig is pulling nicely at 55-plus. He starts up a grade and tromps the accelerator to make the climb. As he tops it and begins down the other side, Joe either fails to see or doesn't recognize two road signs. One says, "Steep Grade, Trucks Gear Down," the other, "45 mph Speed Limit."
Joe finally gets off the gas but he doesn't gear down. His rig quickly picks up speed. Peering through his wipers, he realizes the hill is getting steep and there's a sharp curve ahead.
He jumps on the brake treadle pretty hard, and as expected, his rig starts to slow. Maybe he's down to 50, he doesn't know. With the curve staring him in the face, it's too late to gear down. He doesn't think of it, anyway.
Meantime, Harvey Homeowner and his family are coming up the hill on their way home from a family outing. Harvey knows the road well. He's taking it easy as he climbs the curves, when suddenly, a giant semi is headed right at him. He swerves hard to the right, off the shoulder and into the weeds.
Next thing he knows, he's in the hospital. He doesn't yet know his child is dead. The police find his sedan opened like a sardine can down the left side. The rest, I best not describe.
The police find the driver pulled over a half-mile down the road. When questioned, he's unaware he hit anything. He says he was so busy trying to slow his rig and make the curve that he never looked in the mirror. A later inspection of the rig shows damage to the trailer rear bumper (which ripped open the car) and what appears to be a dent behind the cab door indicating the trailer had swung around so violently it hit the cab.
So what caused the accident? Obviously the driver. But what else? Do you remember the equipment? The new tractor had ABS. The 1997 trailer did not. When Joe braked, probably in panic, the tractor's ABS worked perfectly. ABS probably saved Joe's butt.
But what about the trailer? With no ABS, a slick road and no weight in the trailer, Joe's hard braking locked up the trailer tandem without his knowledge. The trailer swung across the two-lane road like a giant wiper blade. Poor Harvey didn't have a chance.
There is a moral to this horrible accident:
1. Always know if your entire rig has ABS. And if not, which unit doesn't have it.
2. When a rig, or any part of it, is running empty and without ABS, heavy braking invites either a tractor or trailer jackknife.
While driver error caused this tragedy, having ABS on the tractor but not on the trailer led to uncontrolled trailer swing. Ultimately the combined factors killed Harvey Homeowner's child.
Don't forget it.