The idea is simple to implement. The golden rule Turn! You! Turn around! is effective. Anyone who opens a car door - whether sitting in the back or front, as a driver or passenger - should look over their shoulder or in the mirror. So much for the theory!
In practice, drivers are distracted or careless. Sometimes they forget to look over their shoulder in a hurry. The carelessly opened car door then suddenly becomes a cyclist's undoing.
Rapid cyclists may just be able to avoid a confrontation with the car door in this situation. However, they often fall when trying to avoid the door or hit the door, the edge of which is at head height. This type of accident is also known as "dooring".
The remedy for dooring accidents could be a handle from the Netherlands. This so-called #dutchreacharound forces drivers and passengers to look backwards when opening the door, as they have to use their right hand to open the driver's door or their left hand to open the passenger door.
Whoever opens the car door with the hand that is further away automatically turns their upper body to the side and thus into the shoulder view.