From Wazeopedia

Detour Prevention Mechanisms

443 bytes added, 5 years ago
Added note regarding alternate name discontinuities triggering big detour prevention as discussed here:
* 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.
* Be careful where route number concurrencies begin and end as the big detour mechanism may be triggered by discontinuity of alternate names. Where an alternate route exits a freeway or highway over ramps at an interchange, if the ramps do not have the same alternate name as the segments entering and leaving the interchange, the big detour prevention mechanism may prevent routes over the ramps.
==Small Detours==
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.