>
> "There is a wearout mechanism in metal called electromigration. The failure
> typically relates to high current (electrons) moving metal atoms resulting
> in
> voids (missing metal atoms or a hole in the metal line). This failure
> typically
> appears close to the contact area and not in the middle of a wire."
>

If you read the next answer down on Quora, he points out that
electromigration is an issue in integrated circuits, where current density
may be 100,000 amperes per cm^2 -- not in a car wire with density of less
than one ampere per cm^2.

Yrs,
d