I remember reading (a while ago) that adding new lots to a world via World Editor breaks the routing turning your game into a lagapalooza. Unfortunately, I can't track down the thread where I read this (it was on this site) and Google and MTS searches have proven unhelpful. Can someone confirm/deny/elaborate or provide a link to a discussion on this if it has been explored at length?

Some background, I would like to add some more lots and a custom University to a custom world I am playing. Probably not too many, just 4 or 5 new lots as the world is well planned and substantial as is but want to ensure that it's safe to do so first and I won't bork my game by doing so.

Any feedback/direction much appreciated!

The world editor lot tool is still quite broken and yes, it will break the routing of the neighbourhood, either in smaller scale or larger scale. After three worlds gone wonky, I completely stopped using the tool. There are many threads about it, even here at MTS2. Here's one from the official forum: http://forum.thesims3.com/jforum/posts/list/734619.page

Ah, so it's best to stay clear.

Thanks! I never thought about looking at the official forums for help. :p