I've always understood an 'accident' implies an inadvertent contact such that damage or injury was caused. An 'incident' implies to me that damage or injury was not, or probably not caused. There will be blurring of this. Hence:
Any collision involving any vehicles, with or without injury, with each other or any other object- accident
Any near collision, with or without injury- incident.
So an evasive near miss involving passengers being thrown about and hurt- incident. The moment that involved inadvertent contact between the vehicles or with any object- accident (whether injury occurs or not)