Crash To Desktop

A crash to desktop (abbrv: CTD) is the name for when the game unexpectedly closes and returns you to the desktop.

Commonly Known Causes of CTD's

• Zooming out (Expand)
• Making contact between Puzzle Pieces and TE'd Lot's
• Functional Landmarks Mod, while you still have normal, non-functional Landmarks in your city.

others...

Info from SC4D

FAQ This issue occurs only when a Puzzle Piece of a certain network is hovered over a TE Lot that is transit enabled with the same network. For example, Elevated Heavy Rail Viaducts over a Transit-Enabled Rail Station.

The issue is the result of hardcoded material in the main .exe file, so there is no way to fix it. When you select a puzzle piece, be careful that the cursor is not located over a TE Lot. Otherwise, the game will crash immediately without you even noticing that you hovered a puzzle piece over a TE-Lot.

It is, however, possible to avoid it, with a few simple tips:

• Be careful when placing Puzzle Pieces and TE Lots like Stations, Transit Switches, Bus Blockers, etc.
• Avoid using unnecessary Puzzle Pieces. For instance, use Draggable GLR instead of GLR Puzzle Pieces--GLR Stations are TE Lots
• Avoid using unnecessary TE Lots, especially those merely intended for cosmetic purposes--they can also cause issues with the Traffic Simulator

For more info on TE Lots, see mott's discussion on the topic [1].

Technical info: why this problem occurs The SimCity 4.exe file, for some reason or another, tends to get stuck in an "infinite loop" when puzzle pieces are hovered over TE Lots. The infinite loop causes an exception and the game closes itself automatically due to this.

Thanks to Chrisim for providing some additional information on this issue!