Road users such as pedestrians, cyclists and motorcyclists are highly susceptible to crash forces. Yet, while Safe System thinking accords susceptibility to crash forces and a forgiving system as focal principles, the greater vulnerability of these road users is barely recognised in many models of a Safe System. This is a concern of growing importance, given current efforts to increase usage of active travel modes and substantially rising injury rates among cyclists and motorcyclists. This paper explores a selection of research studies aiming to identify relevant factors behind traffic conflicts involving vulnerable road users, as a means to determine appropriate countermeasures particularly those involving infrastructure and vehicle technology. A better understanding of the contextual nature and causes of traffic conflict has much potential to contribute to Safe System thinking and conceptualisations, allowing them to extend beyond their traditional focus on susceptibility to crash forces and systems that are forgiving.