Generally, the person opening the door is at fault and, therefore, liable for all damages. All drivers and their passengers have a duty to exercise reasonable care in opening a car door. The law requires that they refrain from opening a vehicle door unless it is safe to do so. They must also not keep the door open for longer than is necessary to load or unload passengers or cargo. Because of this, liability will often lie with car owners and their passengers in most open car door motorcycle accidents.
The amount of damages awarded will depend on the circumstances. If you were speeding as a motorcyclist, you may share a portion of the blame with the driver. You can still obtain compensation in such a case, but the damages will be reduced in proportion to the degree of your fault.
There are situations when neither the motorcyclist nor the driver are at fault. The accident could have been caused by poor road conditions, of the failure of the government to provide adequate safety measures.