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Roundabouts

234 bytes added, 4 months ago
Fake U-turn prevention: attempting to simplify the description. Added condition #1 for penalty.
====Fake U-turn prevention====
[[File:RA-UTP.png|thumb|The movement from SR-101, through the selected roundabout segment and out to SR-10 is penalized, because the junction angles add up to 180° and the roundabout segment is short and straight.]]One solution is to activate the [[Routing penalties/Controlling U-turn penalties|three-segment U-turn penalty]]. This The Waze routing engine treats the entry to, exit from and the next exit as opposite directions short connecting segment of a divided road, and the roundabout segment interstitial segment are treated the same as though they were the opposing directions and connecting median segment of the a divided road. If the conditions are met, over which Uthe 3-turns are not permittedsegment turn will almost always be prevented. To use:# Make sure that path to be avoided uses 3 segments (in, roundabout, and out).
# Move the nodes so that the roundabout segment is {{:Routing penalties/U-turn minimum|less}} long or less.
# On the entry and exit segments, move geometry points very close to the nodes so that at the roundabout segment, the entry and exit segment are within five degrees of parallel.
#* Note that the algorithm actually measures parallelism and Do not simply depend upon the sum of angles, so it ignores any between the 3 segments unless the roundabout segment is completely straight. You may remove all the geometry points on in the interstitial short roundabout segment when checking for parallelismto check the angles, then undo the change.If all three criteria are satisfied (three segments in the movement, roundabout segment length and parallelism), a large penalty will be applied to the movement into and out of the U-turn, causing routes involving the at-grade connector strongly to be preferred in routingmuch more likely..
Because
This solution is only compatible with non-normal roundabout instructions, as there will be too many nodes to meet the criteria for normal instructions. It's also difficult to use where the entrance of the first road is very far away from the exit of the next road.
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