A tractor-trailer cannot make a curb-tight right turn: the trailer's wheels track far inside the tractor's path, so the driver swings left or starts wide to keep the trailer off the curb. That geometry opens a triangle of space along the truck's right side mid-turn, and the illustrated red car has driven into it.
Both audiences get a rule. The truck driver's: signal early, take the turn the way the manual teaches, and watch the right mirror throughout, because the gap invites exactly this. The car driver's: never slide into the space between a turning truck and the curb; a truck signaling right owns the whole corner until the trailer is through.
The tested mistake is the car's: reading the truck's leftward swing as a lane change and diving up the right side. The trailer then sweeps the space the car occupies, and the car loses.
This situation appears in 18 questions across 17 of our state banks, on Driver License and CDL practice tests. Start with your state:
A large truck swings left while signaling a right turn. Where should you avoid driving?
Why: A commercial vehicle may swing left before a wide right turn, so a motorist must not enter the space between that vehicle and the curb. Therefore, the supported response is "Between the truck and the curb".
Every practice test explains its answers this way. Pick your state and take one free; no sign-up.
Choose your stateThe trailer wheels off-track toward the inside of the turn, so a curb-tight start would put the trailer over the curb, signs, or pedestrians. The wide start is the trailer's turning room.
The space between the truck's right side and the curb mid-turn. The trailer sweeps through it as the turn completes, closing it on anything inside.
Stay behind it, out of the right-side gap, until the trailer clears the corner. The swing to the left is part of the right turn, not an invitation to pass.
An early signal, the taught turn geometry, and continuous right-mirror checks for exactly the car our scenario draws. CDL exams test the mirror discipline as much as the path.
On CDL exams as turning technique and mirror use; on permit exams as the never-pass-a-turning-truck-on-the-right rule. Both read the same picture from different seats.