# Routing penalties/Controlling U-turn penalties

### Median U-turn penalty

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

#### Preventing median U-turns

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

- The U-turn involves a reversal of driving direction through 3 segments:

A) an incoming segment, B) a single median segment, and C) an outgoing segment - Segment B is shorter than 15 m (49.21 feet)
- Segment A and segment B 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 a 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 the median segment B longer than 15 m (49.21 ft)
- To allow a U-turn from only one direction, first set up U-turn prevention for both directions. Then, to allow U-turns on one side, change the angles for segment A and segment B so they 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 the incoming and outgoing segments to be within ±5º of parallel to each other. This is checked by using a *straight* median segment and the Junction Angle Info (JAI) browser extension to measure the angles. JAI may be set for absolute or turn angles; either setting is OK.

If segment B is straight, measure the angles between segment A and segment B, and between segment B segment C. If the sum of these angles is between 175º and 185º, segment A and segment B are considered parallel.

If segment B has geometry nodes it is not straight. It cannot be used to measure the turn angles. Instead, draw a straight segment to the same junctions used by segment B. Check the angles using this straight median. Delete the straight median afterwards