Do wear a seat belt, but not a winter jacket
Research shows that it is dangerous to wear a jacket or thick winter clothes in the car. Mobility organizations advise not to wear a jacket in the car, even when it is cold. The German mobility organization ADAC has carried out laboratory tests on the effects of wearing a jacket in the car.
The test was carried out at a speed of 16 km/hour until an emergency stop followed, which is comparable to a rear-end collision. Because there is a lot of space between the belt and the body due to thick winter clothing, the belt functioning becomes unpredictable. This also applies to children in child seats.
Thick winter clothing restricts the freedom of movement, which is impractical, for example, when looking over the shoulder or maneuvering. Moreover, the combination of warm clothing with the (often high-performance) interior heating – once the engine has reached operating temperature – can lead to reduced alertness or even sleepiness. Passengers can use a car blanket on cold days as long as it is used above the belt.
The seatbelt in a car is a three-point belt because the belt holds the body in place at three points (collarbone, hip left and hip right). If the belt does not fit these (hard) body parts, it cannot hold the body properly in place in the event of an impact.
The body can slide under the belt (submarining effect), causing the upper legs or pelvis to break. A belt that is not in the right place might also damage soft body parts such as the spleen, liver, and intestines causing internal bleeding.