How does the brain calculate velocity? How does the human brain calculate velocities? For example, when crossing a road and seeing a car coming towards you, how does the brain actually compute the rough velocity of the vehicle and your own maximum speed as you cross the road so as to judge that you can cross safely without using the relevant physics equations? I am interested particularly in the specific cognitive and/or neural processes and that level of detail rather than just the fact that the brain estimates distance and time taken to cross that distance. 

N.B. This question is derived from an earlier post of mine which I was advised to split into two for clarity.
Motion perception

This article on motion perception might be a good start.


  pure motion perception is referred to as "first-order" motion
  perception and is mediated by relatively simple "motion sensors" in
  the visual system, that have evolved to detect a change in luminance
  at one point on the retina and correlate it with a change in luminance
  at a neighbouring point on the retina after a short delay


Vehicle velocity

There are a few articles on estimating vehicle velocity.
Scialfa et al (1991) provides a more behavioural account focussing on age differences. 

References

Scialfa, C. T., Guzy, L. T., Leibowitz, H. W., Garvey, P. M., &amp; Tyrrell, R. A. (1991). Age differences in estimating vehicle velocity. Psychology and aging, 6(1), 60. PDF