I have been trying to move villagers around in minecarts lately and have found that powered rails that are deactivated are not slowing down minecarts. Even if I have several connected to each other the cart will just roll on through then pick up speed once on normal rails.

I have also found minecarts can go up a normal rails that is inclined as if it has been powered. I have pushed a villager in a cart onto rails (no powered) that then went up a slope and the cart travelled over 10 blocks without issue, to me this shouldn't be possible.