Added note regarding alternate name discontinuities triggering big detour prevention as discussed here: https://www.waze.com/forum/viewtopic.php?f=8&t=111256
For split roads that have the same name on both carriageways, the big detour prevention mechanism will prevent U-turns that traverse more than one segment. Thus in the intersection below, the configuration on the left will be used to route a U-turn because it uses a single segment between the two parallel roadways with the same name. In contrast, the configuration on the right will '''not''' use the U-Turn road because it branches from another segment causing multiple segments between the two parallel roads with the same name.
Waze has a small detour prevention mechanism to deal with instances where waze calculates that that its a few seconds faster to continue straight or make a right at an intersection and make a u-turn rather than just turning left. Waze will eliminate such detours if there is under a 30 sec difference in the routes.