I had to give up the city. All my moneys went to crime fighting, but traffic kept the police from being effective. I believe a fix would be to just destroy residential and hope that traffic dissipates so the crime can be dealt with.
Also my neighbor caused traffic problems in my city, because he built a gazillion regional buses. There was practically a queue along the whole highway of ONLY buses carrying workers home from his city.
Retrospective, it is kind of hilarious how bad me and my friend managed our first two cities. My friend has an interesting play style, so he managed to first burn down his whole city. He then rebuilt it as an extremely polluted industry city, but traffic problems killed his freight industry and he went bankrupt. What he then did was to almost nuke ALL zones from the city, and focus 100% on mining, buying and selling on the stock market. He managed to be on the top global list of pollution, as well as topping at a whopping 11 on the global list for mining. He had several million dollars, but his wasteland of mining was so crime filled, (half his map was orange), it really fucked mine up. I forced him to give me a shit ton of money and make him build a lot of police.
However, the server acted up, so I never got the money as a gift or the police help. Also, when he went bankrupt, he was forced the close down all his power plants. This caused my city to suddenly have no power, so yeah, it was an interesting session.