That's true, and it also can cause problems with emergency services if not planned out correctly (i.e. the service should always be located somewhere conveniently "upstream" so that they don't need to do gymnastics to get where they need to go).
I will use 2-lane roads in certain areas, but I find that even with the higher volume of traffic, being intentional in preventing the creation of stoplights has helped my traffic flow. There may be more traffic, but it's all moving quickly...
Yeah, preventing any sort of stop or slowdown is very important on the micro level. It's really the main advantage of highways in-game, and not the fact that they could handle more cars.
Personally, the best tips I've found came from that reddit post the RL traffic engineer made (if you haven't seen it already it's one of the top up voted posts of all time on the CS subreddit so you should be able to find it easily). While a lot of his stuff is useful, I think two pieces of advice stands above the others. First, you must design your road system in a kind of "hierarchy", where small levels of roads feed into high levels. Picture since I can't explain it well:
This helps traffic flow in a predictable but controlled manner.
Second piece of advice was that sometimes the issue is not so much your road system but the buildings themselves. To give a more extreme example, if you stuff all your commercial in one corner of your city, you *will* get traffic no matter how well-designed your road network is because you'll get a gazillion cars and trucks going in the same direction. So spreading RCI and mixing them appropriately does wonders because of cars all headed in the same directions they are spread more evenly. Once in my city I was having some noticeable congestion, and it was solved when I replaced a small section of industry with offices - the reduction in trucks in a specific area made all the difference.
I pretty much only followed these two pieces of advice, anyways, and made a very widespread public bus/metro network, and my city of 150000+ that I posted a while back had pretty much no traffic problems. Sure, there were a few areas with heavy traffic, but no congestion. I'm sure I could've gone even further but unfortunately my machine can't handle it.
), the devs have been hinting again at new stuff coming very soon™ which, so far as we know, will be a free patch/update including tunnels, wall-to-wall European-style buildings, and some other big surprise. TotalyMoo posted this screenshot of a tunnel on reddit:
