I just tried my 1st big city with lots of high dense roads (I normally stick to med dense). I'm having the constant issue of service cars coming out their lots to get stuck by overlapping cars already in the street.
I just went to put some food in the microwaves, and came back to see my entire city in the red (traffic grid)! I looked to see what the problem was, and it was a police car stuck on top of another car. 20 mins before that, it was school busess stuck on each other trying to take kids back home at the sametime.
I did learn a small, aggrivating workaround. You have to log out your city and back in to unstuck everything. --- Happyscrub's league of legends rank is higher than 95% gamefaqs posters. This is why gamefaqs jealous of him. That's why they troll him. So sad, So bad, so mad.
I'm using a single long snake avenue in my current city: http://i.imgur.com/khVSck9.jpg
They work. 230k population, less than 10k are using mass transit and no traffic problem. The only 4 way stops are in the industrial area, and even then there is only 3. All traffic that does not intend on entering the city takes the bottom most street across. --- http://www.tf2items.com/id/davidjr