Can you define which of these buses is faster?

In this test, there are two moving rectangles, which we will consider as buses. Can you decide which one is winning the race? See below and draw your conclusions:

Although they seem to be in a race and at different speeds, when the background is in a solid color it is possible to see that, in reality, the two buses were always at the same speed. This test, calledStepping Feet Illusion”, was first described in 2003.

In the first description, made by Stuart Anstis, he said that this is the effect felt by drivers in foggy situations, when the difference between the brightness of the cars and the scenery in the background is less noticeable than on a sunny day. So, as a result, people tend to miscalculate the car's speed, often thinking they are moving slower than they actually are.

At the gif above, when the blue bus is on the white lines, the contrast is high (dark blue on white), which makes it easily noticeable, appearing to be faster than it actually is. The opposite is also true: when the blue is over the black stripes, the contrast becomes low. (dark blue on black), making it harder to see, which makes movement appear more slow.

Thus, the effect that happens with blue can be replicated with yellow, so the sensation is repeated, as if they really were at different speeds, one always ahead of the other. This makes it seem as if they were steps, one in front of the other and vice versa, which is why the name of the illusion is Stepping Feet Illusion, something like "illusion of steps".

But, as said here, all this is just a optical illusion, easily noticeable when the background becomes a neutral, solid color for both. At that moment, we can verify that the velocities are exactly the same.

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