Is it illegal to modify a 4-point seat belt?

[VonDylan]

Modifying a 4-point seat belt is not illegal, but installing a 4-point seat belt requires replacing it with a suitable sports safety seat. Function of 4-point seat belts: A typical 4-point seat belt includes two vertical straps that secure the occupant's chest and connect to a horizontal belt at the bottom. It is called a "4-point seat belt" because it has four attachment points inside the vehicle. 4-point seat belts have been used in racing cars for many years, and some automakers, such as Volvo, are now attempting to apply them to compact cars. Design purpose of 4-point seat belts: The design purpose is to distribute impact forces more evenly during a rollover and to firmly secure passengers in their seats.

[ValentinaFitz]

As an experienced driver, I've seen quite a few cases of modified seat belts. The 4-point harness does look much cooler than regular seat belts, but you need to pay attention to traffic regulations. According to China's "Safety Technical Requirements for Motor Vehicle Operation", mass-produced vehicles must use 3-point seat belts that comply with national standards. If you remove the factory-installed seat belts and replace them with 4-point harnesses, your vehicle will definitely fail the annual inspection, and you'll have to restore them if stopped by traffic police. However, there's a special case: if you keep the original 3-point seat belts intact and install additional 4-point harnesses on the seats (like in racing cars), using the factory belts for daily city driving and the 4-point harnesses on the track, then it's not against regulations. But it's better not to modify the passenger seat and rear seats arbitrarily - safety first, after all.

[EmeryLynn]

Having been in the modification scene for over a decade, I can clearly tell you that installing a four-point harness for street use counts as illegal modification. The key issue lies in the mounting points – factory three-point seatbelts are welded to the vehicle's roll cage structure, whereas aftermarket four-point harnesses you install on seats lack proper structural support and may snap during collisions. I once witnessed a modified car's crash test where the passenger-side four-point harness detached at just 40km/h impact – extremely dangerous. For serious modifications, I recommend professional racing shops. They'll weld a proper roll cage to the chassis before installing certified harnesses, but such modified vehicles essentially become track-only toys with no road legality.

[CarterLee]

Attention to automotive regulations reminds you: Article 16 of the Road Traffic Safety Law explicitly prohibits unauthorized modification of a motor vehicle's registered structure. Seat belts are part of the vehicle's safety structure. There was a classic case last year where a BMW owner replaced the standard seat belt with a four-point harness, resulting in a shoulder strap tear during a rear-end collision that caused rib fractures—insurance companies outright denied the claim. Test data further highlights the issue: in ordinary collisions, the pressure exerted by a four-point harness on the spine is 1.8 times that of a three-point seat belt, with a 47% higher risk of cervical spine injury. It is recommended to retain the factory-installed seat belts. If you seek better body support, consider switching to sports seats—it's much safer than modifying seat belts.