Skylines coming out and everyone going nuts with traffic engineering with the flexible road system was a fun time. Shame that the actual traffic simulation was dogshit with cars all piling up in one lane and forcing the player to design around it. That one thing is actually what made me quit the game before really experiencing much of it because I realized the need to preplan road design (for later even if it wasn't necessary early on) in such a weird way (I think I had meant to build a one-way network with splitting to force traffic to use all lanes) and it was a goddamn fun vacuum.