# 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 52.49 ft (16 m). As a safety margin, leave a 1 meter buffer zone by using 45.93 ft (14 m) or less.
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) 52.49 ft (16 m) 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 is straight, sum the two angles making up the U-turn:

1. The angle between the incoming and median segments (between A and B)
2. The angle between the median and outgoing segments (between B and C)

The in and out segments (A and C) are considered parallel if the sum is between 175º and 185º.

 The 14m median segment in the examples above satisfies condition #2 for U-turn prevention.
##### 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 the median segment (B) and where the median segment (B) junctions with the out-segment (C)). Check the angles using this new straight segment, and delete the new segment afterwards.

 Be sure the junctions are not locked above your rank, otherwise drawing a new temporary segment connected to locked junctions may produce a save error even if it is deleted prior to saving. Click Expand for details on workaround options if any of the segments connected to either junction node are locked above your rank. Disable the WME setting "Draw new roads with all turns allowed" before drawing the new segment. Draw the new segment disconnected from any other segment, then drag the end nodes to connect to the junctions.