Hey guys, you will get more timely (and sorry, occasionally more accurate) answers to some of these NRaas mod questions if you post them on our site. It's kind of what we are there for.
The delta setting in the NRaas Traffic mod only controls the "fake" taxis that roam around for the streets for ambiance. They don't have drivers and no sim can use those for anything. Setting the delta to a highly negative number (-500 should shut that engine down completely for most worlds) does not affect whether sims take "real" taxis to get around. Setting the delta to zero would have no effect at all. Also, the settings are world specific, so what you have going on in Bridgeport does not affect what you have set in China (Barnacle Bay, Dragon Valley, etc.if you use Traveler) within the same game save, although when traveling to a world for the first time within a game, by default that world will inherit mod settings from the place you started. They are still independent settings, though.
There is also a setting in that mod to switch off the game's ingenious
(coughs) issuing of temporary cars to inactives who lack them so they can get around. Invariably those are cheap, awful looking cars that the inactives abandon after a single trip and need to get cleaned up via Overwatch or things get clogged up. Frankly, I would rather see an
occasional taxi in a world where there shouldn't be many if an inactive sim is actually using it to go someplace than have the abandoned cars thing happening.