Daily I come across several more examples where instead of left turn, it wants to go straight through and U-turn back, or do a right, then a U-turn. And fairly common now popping up are instances where instead of going straight, Waze directs to take a right turn, then U-turn, then right again. This type of routing glitch seems to be getting more and more frequent with time. It suggests that either there's a serious problem with the routing engine, or there's a fundamental problem with the current concept of how Waze gets and uses speed information to make its decisions. When traffic gets heavy at an intersection, infrequently chosen alternates are going to start looking more and more appealing to Waze, and because no-one in their right mind would take them, Waze is never going to get a lot of data to refute it's ideas. Waze's problem is that it has no eyes, and can't see what's happening. It's information is indirect and incomplete. It can tell to a limited extent what the drivers do, but cannot tell any information about what they don't do, and has no concept why not. Waze doesn't even really respond when Wazers refuse its instructions, eventually it may raise a flag for someone else to look at, but that's very far removed and indirect, and is not at all responsive to the current situation.
Waze also has a lot of trouble getting good timing data for turns on divided roads. If you are directed to make a left turn at the intersection, you aren't going to turn left at the end of the segment leading up to the intersection, you are going to turn left in the segment in the middle of the intersection. That segment will almost always have good time, because you don't enter the intersection unless you are going to clear it (if you are obeying the law in the US). The backup you have waiting for the light, however, will get lumped in with the straight through traffic, polluting their data making Waze think it's slower to go straight, and the straight through data will pollute the left turn data making Waze think it'll be faster to turn left than it will. This timing data is improved if the intersections are changed to bowties, but that introduces other problems.
Orange County, CA, USA, Samsung Galaxy S3, Android 4.3