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Whether we see a far away car moving at the same speed as a near by car , or we see the road and far away landscape (mountains) moving (backwards) when we move in a car , the far away object always seems to be moving very slowly. I did not ask this on Physics because I think it's answer should be a mathematical proof. It has to be due the bodies rate of change of distance. I hope angle is the suspect.

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    Perspective?... – 2017-01-24
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    https://en.wikipedia.org/wiki/Angle_of_view – 2017-01-24
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    The relative linear velocity is the same for the close and far away objects, so just using some trigonometry it's easy to see that the rate of rotation for the closer object is greater. Hence you perceive it to be moving faster because you have to swivel your eyes/ head faster to keep your focus point. – 2017-01-24
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    @Algorist Only Perspective? – 2017-01-24

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suppose an object is moving at $x$ meter/second horizontally, and this object is moving $1$ metre height above the observer.

So, after one metre, the object can be seen at an angle $\theta_1$ and
$\theta_1 = \tan^{-1}\left(\dfrac{x}{1}\right)$

Suppose the object was moving $100$ metre height above the observer. then,
$\theta_2 = \tan^{-1}\left(\dfrac{x}{100}\right)$

Here, $\theta_2 \lt \theta_1$ means, the heigher the height of the object is, the lesser its speed is to an oberver

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    Here,  theta 2 < theta 1 means, the height the object is, the lesser its speed is to an oberver. Is it the actual speed or the perceived speed because the angle is real not perceived – 2017-01-24
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    It is the perceived speed. – 2017-01-24
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    i think no need to get it confused with the actual speed. there is nothing like actual speed. speed is meaningful only when it is related to one object. – 2017-01-24
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    So it's just the velocity we perceive (not it's relative velocity) – 2017-01-25