Health

Think of your car as a large prosthetic, like those sprung "blades" used by athletes.  Except this one surrounds you, has wheels and a power supply.  Its metal outer shell is like a cranium: devoid of many nerves, so you can't feel your new extremities—in the way a cat can use its whiskers to judge gaps.

The engine is its heart, a pump for the oxygenating fuel delivered from the tank (stomach).  It has a baseline resting rate, but pumps faster when more power is needed by "muscles to move the legs" (i.e. by the gearbox, to twist the wheels).  When in eco-mode it goes catatonic, not dead.  Changing gears is like swapping to longer blades the faster you run.

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Cars moving together (= traffic) are like blood corpuscles, finding their own smaller channels (= side streets) to relieve pressure if a main arterial route clogs up.