From accelerate to brake

Even seen
through the rainy windshield
of a moving car
these shapes have meaning.
Though vision's blurred,
we know we're seeing
three circles in a black rectangle;
we know what to expect,
what lies ahead.
What other signs are there
-- though blurry at a conscious level --
that we subconsciously interpret
as if they're laws?
What else is there
that makes us shift a foot
from accelerate to brake?


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