Why do objects seem to move faster (relatively) when they move tangential to the observer?

I've observed this loads of times while travelling, in cars, trains,etc.I can't quite put it in words and therefore I've roughly made a diagram to assist my question.

Assume an observer is travelling somewhat fast along a path, which has a wall with black and white stripes at the side. (I observed the effect in this exact setting.)

Now look at Case A, here the observer is moving straight at some velocity, and is observing the stripes towards the front of his viewing field. (i.e. viewing through the windshield of the car.) The viewer, of course, views the stripes approaching him at some speed.

For Case B, the observer is moving with the same velocity as above, but now is looking at the stripes which are directly adjacent to him. (i.e. viewing through the window on the side of the car). These stripes, strangely, seem to be moving at a much higher speed than the stripes in Case A!(Black and White seem like a blur, if they were distinguishable in Case A)

Is this an actual observed effect, or have my observations been wrong? Why do the stripes in the second case seem to be moving faster even though everything is practically the same?