# Routing penalties/Controlling U-turn penalties

### Median U-turn penalty

 For the latest discussion on this section please visit the wiki forum thread.

The Waze routing algorithm sets a penalty for some double-left or double-right turns. This can prevent U-turns at H or # style intersections on divided and parallel roads.

#### Preventing median U-turns

An extremely large U-turn penalty is set for a double-left or double-right turn when all three of the conditions below are met:

1. Three segments: The U-turn is a reversal of driving direction through three segments:
an incoming segment (A), a single median segment (B) and an outgoing segment (C).
2. Short median: The median segment (B) is shorter than 15 meters (49.21 feet).
3. In/out parallelism: The in and out segments (A and C) are within ±5° of parallel to each other.

 It is possible for this method to fail to prevent a U-turn when it is the first segment of a route or reroute. If you observe this method to fail when it is implemented properly, please report it in this forum thread

#### Allowing median U-turns

To allow a double-left or double-right turn through the median segment, break any one of the above conditions. For example:

• To allow median U-turns in both directions, break condition #2 by making the median segment (B) 16 meters (52.5 feet) or longer
• To allow a U-turn from only one direction, first set up U-turn prevention for both directions. Break condition #3 on the side where U-turns are allowed. Increase or decrease the angles so that the in and out segments (A and C) are not parallel. A micro-dogleg can be used to change the angle without changing the appearance of segment.

#### Checking for parallel incoming and outgoing segments

Condition #3 for U-turn prevention requires that the in and out segments (A and C) are within ±5º of parallel to each other. This is checked by using a straight median segment as the reference and the Junction Angle Info (JAI) browser extension to measure angles. JAI may be set for absolute or turn angles; using either is OK.

##### Straight median segments

If the median segment (B) is straight, add the angle between the in-segment (A) and median (B) and the angle between the median (B) and out-segment (C). The in and out segments (A and C) are considered parallel if the sum of these angles is between 175º and 185º,

##### Curved median segments

If the median segment (B) has been shaped with geometry nodes, it is not straight and cannot be used for determining parallelism. Instead, draw a straight segment connected at the same in and out junctions (where in-segment (A) junctions with median (B) and median (B) junctions with out-segment (C)). Check the angles using this straight segment and delete the segment afterwards.

Note: Be sure the junctions are unlocked, otherwise connecting a temporary segment to locked junctions will produce a save error even if it is deleted prior to saving.