Sims 3 University- Sims won't load

@jodise11  The travel transition is breaking, repeatedly, and that's why your sims aren't arriving safely.  The only solution other than adding mods is to try to reduce the stress on the game engine as much as possible before the transition and hope that it's enough.

• Empty your sims' inventories as much as possible.  A few items is fine; a hundred is not.
• Use "save as" to rename the save, then quit (without saving) immediately before you want to travel.
• Load the game just to the Main Menu.  Turn off memories, the in-game shopping experience, and the hidden object interactive loading screens.
• Lower all the graphics settings to the minimum.  (You can revert to your normal settings after the travel transition.)  Now quit the game again, without loading a save.
• Delete the five cache files in your game folder in Documents: CASPartCache, compositorCache, scriptCache, simCompositorCache, and socialCache.
• Empty out everything in FeaturedItems as well.
• If you play through Origin, sign in and put Origin in offline mode, then disconnect your computer from the internet—turn off wifi and/or pull the ethernet cord.
• Now launch your game, load the save, and travel your sims right away, as soon as the game clock starts moving forward.

The problem is, you could run into the same issue when it's time for your sims to return home, so at the very least, keep a backup of this save from before University so you can revert to it if necessary.

The mod route involves adding NRaas Traveler, ErrorTrap, and Overwatch.  Traveler replaces the fragile EA travel transition with a much more stable version; ET and OW do cleanup in general.  All three mods work on default settings without any player interference.  If you're worried about the effects on your game, please know that they're some of the most well-tested and reliable mods available for Sims 3.  There's never any guarantee, given how unstable the game can be, but the only times I've seen the mods appear to make things worse are when the saves involved already displayed symptoms of serious corruption.