From Wazeopedia

Routing server

1,246 bytes added, 6 years ago
Turn delays: Added Exit Segment Speed Tracking
Now if 9/10 Wazers go straight through, the average road speed for those drivers is still 60 mph even though 1 Wazers' average speed is only 10 mph. The reason is that the routing engine knows the first 9 Wazers are leaving that segment going straight through to the next segment while the other Wazer is making a turn onto a different segment. This prevents the routing server from avoiding segments that have longer turn lane (or straight through) times to leave the segment compared to the route desired.
<!--[[Image:|right]]-->However, Waze has the ability to separately track the average speed of traffic that passes through a segment, but exits to different segments. In the diagram the traffic flowing through Seg4 is tracked separately based on segment to which it exits. There are then two average drive times for:
* Seg4 to Jnct2 to Seg5
* Seg4 to Jnct2 to Seg6
Therefore any traffic building up on Seg4 that turns right to Seg6 will not affect the route timing for the traffic also using Seg4, but instead turning left to Seg5.
For this reason it is important to keep longer segment lengths before a split in the road if there are traffic backups that only affect one exit or the other. To understand this problem better, consider if we add a short Seg8 between Seg7 and Jnct4. Let's say the traffic exiting Seg10 backs up all the way to Seg7. Because Seg7 only has a single exiting segment (Seg8), the routing server is only able to collect a single average speed. Now the through traffic going to Seg9 "appears" to slow down through Seg7. At a minimum this will cause an incorrect ETA for routing, but it might actualy cause traffic to be rerouted unnecessarily through another route.
===Waze Map Editor changes===