Ok, its quite odd. I have my city connected with it's neighbor city. There are several subway, monorail, roads, railways and avenues connections (like 5 avenues). One day i suddenly noticed HUGE lag Problems on my city (ONLY on this one !). I could barely move my mouse and it took like 5 minutes to pass a month on fastest speed. After many hours of having no idea why that lag happens i finally found that ONE avenue that connects the city to its neighbor causes this lag. if i kill the avenue, lag is completly gone! if i rebuild its there again . It's not like the avenue is in high commute use. just like ~10ppl do even use it. I had EXACTLY the same problem on another REGION! 2 citys connected with several roads/avenues and exactly ONE avenue (which isnt even used alot) causes INSANE lag on one of my cities.  I use SC4 Deluxe Edition last patch, got an high-end PC (usually it can easy take cities up to 1million citizens), and few Plugins(NAM). Problem remains if i delete the plugins so i dont think its relevant to list them. Maybe someone has experienced the same and can tell me why this happens. Whats the special thing about those avenues and how can i fix them ?   TXH alot (Screenshot shows the "lag avenue")