can a car drive under a semi

[DeclanMarie]

No, a standard passenger car cannot safely drive under a semi-truck. Attempting to do so is extremely dangerous and will almost certainly result in a catastrophic crash. The clearance between the bottom of a semi's trailer and the road is far less than the height of a car's roof. This is not a stunt you see in movies; in reality, the car's windshield and roof would impact the trailer's underside, likely causing the trailer to crush the passenger compartment with fatal consequences.

The primary factor is undercarriage clearance. A typical semi-trailer's ground clearance is about 4 to 5 feet (48-60 inches). In contrast, the average height of a passenger car is around 4.5 to 5.5 feet (54-66 inches). There is simply no physical space for the car to pass underneath. Even if a truck is raised on its suspension or a car is particularly low, the margin for error is zero.

These incidents, often called "underride crashes," are some of the deadliest on the road. When a car slides under a truck, the trailer's frame bypasses the car's front-end crumple zones and directly impacts the windshield and roof, which are not designed to handle such force. The Insurance Institute for Highway Safety (IIHS) has conducted extensive research on underride guards, the metal bars installed on the back and sides of trailers to prevent this exact scenario. While modern guards help, they are not infallible, especially in side-underride situations.

| Underride Crash Statistics (NHTSA & IIHS Data) | | :--- | :--- | | Fatalities in large truck crashes (2019) | 5,005 | | Passenger vehicle occupant deaths in those crashes | 67% | | Significant underride involved in rear-impact crashes | 45% | | Risk of death in an underride crash vs. other truck crashes | Twice as high | | IIHS-rated "Good" rear underride guards (on new trailers) | Significantly reduce crash severity |

The best advice is defensive driving. Never assume a truck driver can see you. If a truck is turning, do not try to squeeze between it and the curb. Always maintain a safe following distance and never stop directly behind a semi where the driver cannot see you in their mirrors. Your safety depends on understanding the immense size difference between your vehicle and a commercial truck.

[DiCamilla]

It's a firm no. Think about it: your car's roof is level with the trailer's rear bumper. To go under, your car would have to be less than four feet tall. Even a low-slung sports car is too tall. The metal underside of the trailer would smash straight through your windshield. It’s one of the quickest ways a bad decision turns into a tragedy on the road. Just don't ever consider it.

[Nellie]

From an engineering standpoint, the geometry makes it impossible. We measure a vehicle's sill height and ground clearance. A semi-trailer's frame sits at a specific height, while a car's roof has its own. These two measurements overlap significantly. There is no scenario where the car's highest point is below the trailer's lowest point without the car being partially crushed first. The structures are not designed to interact that way; it's a direct and violent collision.