[onecommentman]

Not precisely to discourage unsafe driving. Simply to slow vehicles for any one of several reasons, safety often being an important one. Traffic calming has other benefits, such as more livable residential neighborhoods, and less congested residential side streets, especially during rush hours.

That does have the result of increasing trip times by cars, and thus motivating use of public transit.

Guessing intent is a fool’s game, and can’t really be true or false per se. It does antagonize automobile drivers and, from their valid but particular perspective, makes their life worse in (what would seem to them) a gratuitous fashion. Americans don’t like arbitrary and capricious as a whole.