What are the formal principles of math and physics that describe this scenario? Most local laws require bicyclists to ride with (i.e. in the same direction as) traffic. The rationale behind this is that as a car and a bike are traveling in the same direction the car has more time to react to the bike before overtaking it (when compared to the bike and car traveling towards each other). So how would you describe this in terms of the formal scientific principles involved? Please use very specific terms, and tell me how exactly they describe the above. Thanks!