Why are there such similarities between transportation by cars and the venous system of the body?

Answer 1

my what a odd question. Are you meaning that in the case of transportation in and out of a city as an analogy to blood going in and out of the heart. In that case it may be because a strong work centre has standardized times when people leave or events when people leave in large numbers. This is like a circulatory pump driving the cars away from the centre to the arterial roads to the smaller streets which act as capiliaries to get the people to their cells or homes.