Difference between revisions of "Routing penalties/Controlling U-turn penalties"

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({{@|Allowing median U-turns}})
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* 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 [[#Checking for parallel segments|not parallel]]. A [[Glossary#mDL|micro-dogleg]] can be used to change the angle without changing the appearance of segment.
 
* 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 [[#Checking for parallel segments|not parallel]]. A [[Glossary#mDL|micro-dogleg]] can be used to change the angle without changing the appearance of segment.
 
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[[File:U-turn selective Uturn prevention.png|center]]
  
 
==== {{@|Checking for parallel incoming and outgoing segments}} ====
 
==== {{@|Checking for parallel incoming and outgoing segments}} ====

Revision as of 05:24, 30 September 2015

Median U-turn penalty link to this section

For the latest discussion on this section please visit the wiki forum thread.
U-turn Roads.png

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 link to this section

A 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) or shorter.
  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 link to this section

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.


U-turn selective Uturn prevention.png

Checking for parallel incoming and outgoing segments link to this section

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 link to this section

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). If the sum of these angles is between 175º and 185º, the in and out segments (A and C) are considered parallel.
U-turn Parallel Check Straight.png

Curved median segments link to this section

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 give a save error even if it is deleted prior to saving.
U-turn Parallel Check Curved.png

Additional examples link to this section

Example Tip Details
U-turn example 2mediansegs-bdp.png Cutting a median segment into two may have unintended consequences U-turns are legal at this intersection. While U-turn prevention is not triggered here, Waze will rarely route a U-turn at this intersection. When the railroad was junctioned with the median segment, it cut a single median into two. The two segment discontinuity between divided roads of Major Blvd will trigger a lower penalty mechanism designed to discourage detours off the main road(Big Detour Prevention, BDP).
U-turn example 2mediansegs-allowed.png Cutting a median segment into two may have unintended consequences U-turns are not legal at this intersection, but Waze may route a U-turn here anyway. Cutting the median breaks condition #1, so U-turn prevention will not trigger. Unlike the railroad example, BDP will not trigger here, since the divided east and westbound roads do not have matching primary nor alternate names.
U-turn example curvedU.png A median segment longer than 15 m (49.21 ft) will always allow a U-turn While condition #3 requires a straight segment for determining parallel in and out segments, condition #2 is the measure of the length of the median segment itself. Be careful when the space between divided roads is small. Ensure the U-turn segment is longer than 15 m (49.21 ft) by adjusting its geometry. Conversely, a median segment of any shape can trigger a U-turn penalty if it is not long enough.
U-turn example parkinglot.png To ensure proper routing between two closely spaced parallel roads, connect the two with a segment longer than 15 m (52.5 ft) U-turn prevention triggers for both double-left and double-right turns over any road type. If the three conditions for median U-turn prevention are met, a large penalty will be applied, irrespective of whether the turn is onto the same road in the opposite direction or onto a completely different road. Both double-left and double-right turns can be penalized, regardless of country, and can occur on one way or two way segments.