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Junction Style Guide/Interchange

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An '''interchange''' is a road junction where two traffic can move between roads are connected by dedicated roadways, called '''ramps'''that do not intersect. The roads are connected by an interchange do not intersect one another directlyramps, and if they cross, the crossing is grade-separated. They are most commonly used where one or more roads is a controlled-access highway. Complex interchanges may contain many highways and local roads meeting within small areas. Many different layouts have been developed by traffic engineers to optimize interchanges for size, complexity, traffic safety, navigation, and unimpeded traffic flow.
Since interchanges often involve grade-separated crossings, the [[road elevation]] of the segments becomes important. If two roads cross without connecting directly, their elevations must be different. This article is a sub-article of the [[Junction Style Guide]]. As such, '''this article is a Style Guidestyle guide''' as well. Representing interchanges on the map can be exacting and difficult. The guidance on this page will help editors to create accurate and usable map versions of these interchanges. The following sections discuss the proper style for ramps, interchanges, and some common Interchange interchange designs. Note that some interchanges may be a hybrid of these basic designs where one side or quadrant of the interchange may differ from the others. Also note that since interchanges often involve grade-separated crossings, the [[road elevation]] of the segments becomes important. If two roads cross without connecting directly, their elevations must be different.
Before reading through this article, be sure to fully understand the information in the [[Junction Style Guide]].
== Ramps ==
Ramps have a very specific purpose in Waze. They are intended to connect segments of Minor Highwaysminor highways, Major Highwaysmajor highways, and Freeways freeways to roads where there are no at-grade crossings.
The {{Ramp}} type is used extensively in interchanges for three reasons.
* Ramp segment names are not displayed on the map. This * Ramp segments have essentially no penalty, so they can be used to connect Freeways freeways and Major Highways major highways with each other without causing problems.* Ramp segments are relatively small thin but show at high wide zoom levels, so interchanges do not distract from highways but can be seen at high speeds.
=== When to use ramps ===
Use of the {{Ramp}} type is governed by the following rules:
* [[Road types/USA]]
* [[At-grade connectors]]
=== Ramp geometry and complexity ===
When placing [[File:exitcomparison.png|thumb|Divergence is 12.5° on the left and 22.5° on the beginning of a rampright. No angle between outgoing segments should ever be less than 20°, place to facilitate closure reporting.|250x250px]]This section concerns the first [[geometry node]] of the ramp segment ramps at basic exits and entrances, which are the point where majority of use cases for ramps. For information on the solid white line beginsgeometry of other junctions involving ramps, and extend the ramp naturally to create a junction with see the road segment, typically at a 10–15° angle. This will allow for consistent timing of exit instructionsother sections below.
When placing the beginning of an exit ramp, first place a [[geometry node]] of the ramp segment at the nearest point to the exit from among: * If there's no solid white line, at the gore point (where the painted lines diverge)* If there's a solid white line, at its beginning* The beginning of the inside solid white line on a multi-lane exit* 1/4 mile before the gore point, on exits with a longer solid white line* Halfway between the gore points of the exit and the previous exitExtend the ramp naturally to create a junction with the road segment at a 20° departure angle. This will allow for consistent timing of exit instructions and make it easier to report closures in the Waze client.[[ImageFile:ExitExitRampShort.png|900px]]At the end of an entrance ramp place a geometry node at the end of the solid white line and extend the ramp to join with the highway at a reasonable departure angle that follows the natural road geometry. The angle used should allow for smooth and consistent auto-zoom functionality—the client remains zoomed in for the duration of the ramp-geom, zooming out when the user gets on the freeway.[[File:EntranceRamp.png|900px]]
Do the same when placing Rule #1 is still simpler is better. If there is no large distance between paths at the end of a ramp. This will allow for consistent auto-zoom functionality—the client remains zoomed in for the duration (either into or out of the ramp), zooming out when the user gets on the freewaya single segment connecting to a single junction node is all that is needed. The existence of a painted, concrete, or grass island is '''not''' enough of a reason to divide a ramp into multiple ramps.
: [[ImageFile:Entrance-ramp-geomJunction_style_simple_ramp_(2).pngPNG|400px]]
Rule #1 is still simpler is better. If there is no large distance between When paths at the end of a the ramp (either into or out deviate significantly in distance, regardless of the ramp), a single segment connecting to a single junction node is all that is needed. The existence of a painted, concreteany type of island, or grass island is '''NOT''' enough of a reason to split a ramp into then multiple rampsshould be used.
: [[ImageFile:Jct_ramp_no_splitJunction Style ramp split.pngPNG|350px]]
When paths at == {{anchor|Interchange types}}Component junction types ==Interchanges are made up of multiple individual junctions involving the end of following:* One or more highways, represented by the ramp deviate significantly in distancethree highway road types {{Minor Highway}}, {{Major Highway}}, regardless and {{Freeway}} * Grade-separated cross streets which may be highways or lower road types such as {{Primary Street}} * {{Ramp|Ramps}} to join themSpecific examples of how to handle common junction types are provided in the existence following sections. All of any those examples use these road types. If you are unsure what road type of islandyou should use, then multiple ramps should be usedrefer to the [[road types]] article.
: [[Image:Jct_ramp_split=== {{anchor|Exits}}Basic exit/entrance ===A basic exit is a junction where a single ramp exits a highway and leads to another road, and the continuation of the highway is obvious to drivers. Most exits fit this description.png]]
== Interchange types ==To map a basic exit:These are junctions involving # The entering segment and the three Highway/Freeway road types - continuing segment must be {{Minor HighwayFreeway}}, {{Major Highway}}, and or {{FreewayMinor Highway}} -- as well as their type and should match name and type.# The freeway/highway continuing segment should have close to a zero degree departure angle from the entering segment.# The exiting segment should be of the type {{Ramp|Ramps}}.# The ramp geometry should be consistent with [[#Ramp geometry and complexity|ramp geometry and complexity]].
Specific examples of how When those conditions are met and the ramp exits to the right, the navigation will present an "exit right" instruction when the ramp is to be used, and will remain silent when the continuing freeway/highway segment is to handle common junction types be used. When those conditions are provided met and the ramps exits to the left, the default instruction in later sectionsthe USA is "keep left. All of those examples use " A [[Turn instruction override#Exit left|turn instruction override]] should be used to provide an "exit left" instruction at basic exits where the exit ramp departs the highway to the basic building blocks provided hereleft.
If you are unsure what road type you Similarly, a basic entrance is where a single ramp joins an existing highway, and the path of the highway is obvious to drivers. The geometry of a basic entrance junction should usebe mapped just like a basic exit, refer to the following pages for more informationbut with directions reversed.*[[Road_Types_(USA)|United States]]*[[How_to_label_and_name_roads_%28United_Kingdom%29#Road_types|United Kingdom]]
=== Exits ===It is a basic {{anchor|Exit situation when a "straight" direction is obvious to a driver and navigation instructions are only needed for the non-straight direction (the geometry}}Basic exit.) If navigation instructions are required for both directions, see the [[#Wayfinder_Segments|Wayfinder Segments]] section below. ==== Exit geometry ====
: [[Image:Jct_fwy_exit.png]] [[Image:Jct_maj_exit.png]] [[Image:Jct_min_exit.png]]
To be treated as a basic Exit, the following must be true:See [[# The entering segment Ramp geometry and complexity|ramp geometry and complexity]] for information on setting the continuing segment must be angles of basic exits.==== {{Freeway}}, {{Major Highwayanchor|Exit naming}}, or {{Minor Highway}} type,Basic exit naming ====# The Freewayhighway/Highway continuing segment freeway segments before and after the junction should have close to a zero degree departure angle from be named the entering segment,# same. The other exiting segment must ramp segments should be of named in accordance with the type {{Ramp}}section on [[Road names#Exit|exit ramp names]]. In addition, and# The Ramp exiting segment should have if an exit carries a departure angle around 10–15 degrees concurrent route away from the entering segmenthighway, for example a US route that was carried by an interstate up to the exit but splits off at the exit, that route designation should be added as explained abovean alternate name on all ramp segments that carry it.
=== {{Anchor|Wayfinders|Terminology|Criteria|Configuration|Segment naming}}Complex exit ===A complex exit is a junction where one or more exit ramps leave the highway, and the continuation of the highway is not obvious to drivers. Therefore, another instruction is needed for traffic continuing on the highway. This can be a "keep" or "continue" instruction. When those conditions are metmapping complex exits, the navigation will present an geometry should match the instruction given, so for "Exit Right/Leftcontinue" instruction when instructions the geometry should be set up as described for exits in [[#Ramp geometry and complexity|ramp is to be usedgeometry and complexity]], and will remain silent when for keep instructions (i.e. most wayfinder exits), the geometry should be set up in the continuing same way as a [[#Freeway/Highway segment is to be usedfork geometry|freeway fork]]. For criteria and further details on mapping complex exits, see [[wayfinder]] and [[turn instruction override]].
==== Exit naming ={{anchor|Freeway/highway splits|Freeway/highway forks}}Freeway/highway fork===The HighwayA highway/Freeway segments before freeway fork is a junction where one freeway or highway splits into two, and after the junction should be named there is no obvious straight through direction for a driver. This can happen at the sameend of a concurrency of highway routes or where one or both highway routes begin. The ramp segments should be named in accordance This is synonymous with the best practices in your locationMUTCD term "split."
[[Road names/USA#Exit_ramps_and_Entrance_ramps_.28on-ramps.29|US Specific Ramp Names]] [[How_to_label_and_name_roads_%28United_Kingdom%29#Ramps_.28to.2Ffrom_Motorways_and_Dual_Carriageways.29|UK Specific Ramp Names]] [[Road types and names|Naming standards for other areas]] Editors covering areas that do not have specific best practices should review the existing guides for other areas, and determine which best matches the roadways of your area. === Freeway/highway splits ===A Highway/{{anchor|Freeway Split is when a Highway/split geometry}}Freeway segment meets at a junction with two other Highway/Freeway segments and there is no obvious straight through direction to a driver.  ==== Freeway split fork geometry ====
: [[Image:Jct_fwy_fwy_split.png]]
To receive a navigation instruction for '''both''' branches Place the first geometry node of each outgoing segment at the beginning of a split, the following must be true:# Both exiting segments must be solid white line where the same type (Freewayroadways diverge, Major Highway, Minor Highway).# Each exiting then move the junction node to where each outgoing segment must have a name which is different deviates from the name of the entering incoming segment20° right and left.# The two exiting segments should have departure angles around 10 to 15 degrees from the entering segment.==== {{anchor|Freeway split naming}}Freeway fork naming====
With those conditions metThe purpose of freeway fork naming is to give instructions for both right and left side of the fork that are accurate to posted signage. That can be accomplished using the following:# Signs and [[wayfinder]]<nowiki/> stub segments: If an outgoing segment has a big green sign (BGS) above it that says something different than the name of the entering segment, cut the junction will present "stay segment at the fork to create a stub and name it according to what is on the sign. If the outgoing segment continues the route designation of the incoming segment, add that as an alternate name of the stub to preserve name continuity for [[Detour Prevention Mechanisms|detour prevention]] purposes. If the BGS doesn't say anything different from the name of the highway itself, there is no need to make a stub; simply name the outgoing segment with the name of the highway.# A [[turn instruction override]]: If one branch is named the same as the entering segment either as a primary or alt name, use a turn instruction override to give a "keep left" and or "stay to the keep right" navigation instructions using instruction depending upon which direction the branch leaves the name of fork.For further details on freeway fork mapping, see the appropriate exiting segment[[wayfinder]] page.
==== Freeway split naming ={{anchor|Ramp-ramp forks}}Ramp fork ===A ramp may itself fork and branch into two directions. This is synonymous with the MUTCD term "bifurcation." Most of the time a ramp fork should be mapped to give instructions to traffic going either direction. This is accomplished by using the ramp type for both outgoing segments and names that are different from the incoming segment or turn instruction overrides where necessary.
The primary rule is that all 3 segments at the junction must have different names==== Ramp fork geometry ====[[Image:Jct_ramp_ramp_split.png]] [[Image:jct_cd_ramp_split. png]] That can be accomplished in one of two ways:Ramp forks should generally have the same geometry as [[# Using road names alone - It is an easy situation if all three roads which connect have different names. If "Highway A" splits into "Highway B" and "Highway C"Freeway fork geometry|freeway forks]], then that except for where the ramp fork is all we need to have part of a properly functioning split.# Using signs and [[#Wayfinder_SegmentsCollector/distributor cloverleaf|Wayfinder Segmentscollector/distributor interchange]] - If or if one side of the branches of the split has the same name as the entering segment, we must create uniqueness at the junction. If ramp fork is using a "Highway Xcontinue" splits off from "Highway Y" and "Highway X" continues as instruction or no instruction. In this case the other branch, the preferred approach is to use named ramp fork should look more like a [[#Wayfinder_SegmentsRamp geometry and complexity|Wayfinder Segmentsbasic exit]].
=== Wayfinders =Ramp fork naming ====Naming of ramp forks should generally follow the guidelines from [[Road names#Exit|road names]], but there are multiple ways to handle all the signs present at each junction.
===== Using information on the signs directly =====A '''wayfinder''' gives a user an instruction reminding them simple way to stay on name the road the user ramp segments in ramp forks is already to name each ramp segment with full or abbreviated information shown on, in situations where the signs leading into it. This will provide a reminder is warranted. A wayfinder is warranted in the following situations:* '''Lane drops''', where at least as many lanes leave the road static set of instructions for users as stay they travel on the road;* '''Non-obvious continuations'''each segment, where at least one "exit only" lane exists on the side regardless of the road where exits are not normally placed (in what their further movements will be. This is especially appropriate when a [[right-hand traffic]] country, exiting traffic single sign is to the left and continuing traffic is to the right); and* '''Inconsistent signage''', where a highway continues as a numbered routepresent at an exit, but multiple signs call it only by a namewith different information are present farther down the road.
{{NeedImage===== Using road name inheritance =====[[File:RampforkMUTCD.png| Need sample images for "lane drops" and "non-obvious continuations"; also, example of BGS with lane arrows}}thumb]]
[[File:FreewayS-inS-outAnother way to name these ramp segments is to use name inheritance. If a ramp is unnamed ("no name" box checked), the name of a subsequent ramp on the route will propagate backwards in navigation instructions. This is useful both for the sake of simplicity and for giving more specific instructions to traffic at exits with ramp forks.png|200px|right]]In these casesIf an unnamed ramp is used at an exit and subsequent named ramps are used after the fork, we drivers will only see the name of whichever side of the fork they need to use go to before they exit the highway. This method will provide more sufficient notification of an approaching decision point than a named exit ramp would, and it should be used as long as the names of both ramp forks are visible on signs at the start of the initial ramp. If an exit ramp has multiple lanes with a sign or part of a sign over each lane, using this method can even function as a wayfinder configurationform of lane guidance. If the example on the right from the MUTCD were mapped using name inheritance, the ramp exiting I-42 would not be named. Each wayfinder configuration will have one The ramp that goes to I-17 southbound would be named "INExit 36: I-17 S / Portland" segment and two the ramp that goes to I-17 northbound would be named "OUTExit 36: I-17 N / Miami." segmentsThis would produce the following instructions:* Traffic heading south on I-17 would receive*# at the exit: exit right to Exit 36: I-17 S / Portland*# at the fork: keep right to Exit 36: I-17 S / Portland* Traffic heading north on I-17 would receive*# at the exit: exit right to Exit 36: I-17 N / Miami*# at the fork: keep left to Exit 36: I-17 N / MiamiNote that even though the exit number is by design not shown on signs at the ramp fork, it should be included in the names of the ramps for proper instructions at the exit. If signs at the ramp fork differ more significantly from signs at the exit, a different method of naming should be used.
====== Name inheritance, but signage on consecutive signs are different ======
[[File:PseudoWF.png|thumb]]
Keep these basic principles in mind:* The OUT segments must be If separate or split signs exist for traffic at an exit, but the signs at the same type (either Freeway ramp fork differ significantly from them, such as being further split or showing additional route numbers or Rampcontrol cities, as explained below).* Each OUT segment must have a name different than the IN segment.following method can be used:* OUT segments should be named with the information displayed on # Leave the roadway signs.exit ramp unnamed** However, if this would leave an OUT segment with # At the same name as the IN segment, ramp fork create a turn instruction override for no instruction going into a stub ramp segment naming must be modified in one of the following ways {{u|''in order of preference'':Segment length/Minimum}}:**#Add a control/destination city, if it is known, Name the stub according to the OUT segment name.sign at the ''exit''**#Remove At the junction of the compass cardinal from stub with the OUT next ramp segment name.**#Add create a space turn instruction override to match the end of the OUT segment name (note that this will be flagged by expected instruction at the [[Community Pluginsramp fork, Extensions and Tools#WME Validator|WME Validator script]], if active, and possibly result in undoing by another editor)either keep left or right**#Create a stub in Name the IN next ramp segment just before according to the sign at the junction with no street name.**#*''ramp fork'NOTE:''' This option should only be used as a last resort because or leave it prevents unnamed to inherit farther ramp namesBecause of name inheritance, the shortness of the stub, and the [[Routing server|routing server]] from properly calculating [[Turn delays|combination of turn delays]]instruction overrides, and may result the name of the stub will be used in inefficient routing through the area.* Do '''not''' use "to" instructions at the beginning of exit, and the name of the continuation segment (ramp past the user is already on stub will be used at the road, not going "to" it)ramp fork.* Each "stub" segment This method should only be {{:Segment length/Minimum}} long. This is long enough so used when it will 's not cause routing problems, but it is short enough possible to suppress display of the names (replicate what drivers see on Freeway stubs) and keep freeways looking contiguous (on Ramp stubs)guide signs using simple naming or name inheritance.
== {{Anchor|Interchange configurations}}Configurations ==
To configure the wayfinder, * If the numbered/signed exit is on the '''right''', the OUT segments should be === {{Rampanchor|Diamond interchange}} type. This will give an "exit right" instruction for the exit and a "stay to the left" instruction for the continuation. Diamond ===** For a basic : [[Junction Style Guide/Interchanges#Exits|exit]], use a named Ramp stub for the continuation, and a standard Ramp for the exit.** For a [[Junction Style Guide/Interchanges#FreewayFile:Diamond interchange.2Fhighway splitsPNG|freeway split750px]], use a Ramp stub on both sides.* If the numbered/signed exit is on the '''left''', the OUT segments should be {{Freeway}} type. This will give "stay to the" instructions on both sides (if Ramp segments were used, Waze would give a confusing "exit right" instruction for the continuation).** For a basic See also: [[Junction Style Guide/Interchanges#ExitsWikipedia:Diamond_interchange|exitDiamond interchange article on Wikipedia]], use a named Freeway stub for the continuation, and an unnamed Freeway stub followed by a named Ramp for the exit.** For a [[Junction Style Guide/Interchanges#Freeway.2Fhighway splits|freeway split]], use named Freeway stubs on both sides.''
<div style="font-size:smaller">{| class="wikitable" style="text-align:center"|-! Exit direction! Type! Left OUT configuration! Right OUT configuration! Example|-| Right| Basic exit| '''Continuation side'''<br/>{{Ramp|Named Ramp stub}} → {{Freeway|Named Fwy}}| '''Exit side'''<br/>{{Ramp|Named Ramp}}| [[File:RightExitRampCommon in wide open spaces where land acquisition and geography are not concerns, this interchange design has ramps equally distributed across all 4 quadrants.png|190px]]|-| Right| Fwy split| '''Continuation side'''<br/>{{Ramp|Named Ramp stub}} → {{Freeway|Named Fwy}}| '''Exit side'''<br/>{{Ramp|Named Ramp stub}} → {{Freeway|Named Fwy}}| [[File:RightExitSplit.png|190px]]|-| Left| Basic exit| '''Exit side'''<br/>{{Freeway|Unnamed Fwy stub}} → {{Ramp|Named Ramp}}| '''Continuation side'''<br/>{{Freeway|Named Fwy stub}} → {{Freeway|Named Fwy}}| [[File:LeftExitRamp.png|190px]]|-| Left| Fwy split| '''Exit side'''<br/>{{Freeway|Named Fwy stub}} → {{Freeway|Named Fwy}}| '''Continuation side'''<br/>{{Freeway|Named Fwy stub}} → {{Freeway|Named Fwy}}| [[File:LeftExitSplit.png|190px]]|}</div>
=== Ramp-ramp splits ===A ramp may itself split and branch into two directions. If this is the case, "Exit Right" and "Exit Left" will be announced using the name of the appropriate exiting segment in all cases. ==== Ramp split geometry ====: [[Image:Jct_ramp_ramp_split.png]] ==== Ramp split naming ====If ramps are unnamed, the name of a subsequent ramp will propagate backwards. In the example abovesimplest form, if the two ramps exiting the junction are named, the ramp entering the junction this can be left unnamed. Then any navigation instruction directing you onto the first ramp would use the name of the appropriate exiting ramp. '''Example:''' The two ramps exiting the junction are named "DestinationLeft" and "DestinationRight". The ramp that enters the junction is unnamed. If you need to "Exit Right" onto the unnamed ramp. If you are headed to "DestinationLeft", navigation would tell you:* Exit Right to Destination Left* Exit Left to Destination Left Using unnamed ramps is very useful to provide sufficient notification of an approaching decision point, represented as long as the names of both ramp splits are visible on signs at the start of single connections from the initial ramp. '''Example of good use of unnamed ramps:'''* Initial Exit Sign: to City A and City B* Destination Left Sign: to City A* Destination Right Sign: to City BResult: An unnamed initial ramp will provide accurate and informative navigation instructions to the driver. '''Example of poor use of unnamed ramps:'''* Initial Exit Sign: to Downtown* Destination Left Sign: to Downtown* Destination Right Sign: to Center StResult: An unnamed ramp may create confusion since both Destination ramp names are NOT listed on the initial exit sign. In this case the initial ramp should be named. '''Example of modified use of unnamed ramps:''' * Initial Exit Sign: Exit 70A-B to City A and City B* Destination Left Sign: to City A* Destination Right Sign: to City B* Destination Left name in Waze: Exit 70A: City A* Destination Right name in Waze: Exit 70B: City BResult: By using a modified name for the destination ramps, we have combined information from two sets of signs to generate the advance notice a driver may need to prepare for a decision pointsurface street.
== Interchange configurations ==Please see The straight through motion from the [[Limited_Access_Interchange_Style_Guide|Limited Access Interchange Style Guide]]exit ramp to the entrance ramp should typically be enabled, if legal to drive. Under normal circumstances, the big detour prevention mechanism discourages the routing server from routing someone off the freeway and directly back on. When the freeway path between the ramps is closed, or slow enough to overcome the Detour penalty, this off-on route may be given as a desirable alternative.
=== Diamond interchange ===: Be aware that the big detour prevention penalty is intended to discourage routing that leaves a freeway (or highway) and returns to the same freeway (or highway). Therefore, at least one name (primary or alternate) of the freeway/highway segment before the exit ramp must exactly match one name (primary or alternate) of the freeway/highway segment after the entrance ramp to trigger the penalty. For further information see the [[Image:Jct_diamond.pngDetour Prevention Mechanisms|big detour prevention mechanism]]''See also: [http://en.wikipediapage.org/wiki/Diamond_interchange Diamond Interchange article on Wikipedia]''
Common in wide open spaces where land acquisition and geography are not concerns, this Interchange design has ramps equally distributed across all 4 quadrants:[[Image:Jct_diamond_simple_turns_new.png]]
In the simplest form, this can be represented as single connections from the ramps to the surface street.  Note: Be sure to restrict the straight through motion from the exit ramp onto the entrance ramp on the other side of the road. This will prevent the routing server from trying to route someone off the freeway just to get back on it. Even though it may be a legal direction for a vehicle, turn restrictions are only for controlling routing directions. : [[Image:Jct_diamond_simple_turns.png]] If the ramps connect to the surface street at multiple points, ramp-to-ramp routing should be avoided as well as illegal restrict turns which should use another ramp. Review the section on [[Junction Style Guide/Interchange#How complex should ramps be?Ramp geometry and complexity|How complex should ramps be?ramp geometry and complexity]] in the Junction Style Guide for more details on this topic.
First we see the turns that must be restricted for the exit ramps:
: [[Image:Jct_diamond_cplx_turns_off_LJct_diamond_cplx_turns_off_L_new.png]] [[Image:Jct_diamond_cplx_turns_off_R.png]]
Then we see what must be restricted for the entrance ramps:
: [[Image:Jct_diamond_cplx_turns_on.png]]
'''Note on elevationselevation:'''
The single surface street segment between the inner most ramps should be either raised or lowered in relation to the freeway segments depending on the actual geography at the interchange.
=== {{anchor|Cloverleaf interchange }}Cloverleaf ===
: [[Image:Jct_cloverleaf.png]]
''See also: [http[wikipedia://en.wikipedia.org/wiki/Cloverleaf_interchange |Cloverleaf Interchange article on Wikipedia]]''
In a Cloverleaf cloverleaf Interchange, left turns are eliminated from all movements between the Freeway freeway and the surface street. First check the exit ramps.
: [[Image:Jct_cloverleaf_off_outer_turns.png]] [[Image:Jct_cloverleaf_off_inner_turns.png]]
: [[Image:Jct_cloverleaf_on_turns.png]]
The connections to the Freeway freeway segments may be treated in two ways:
:[[Image:Jct_cloverleaf_options.png]]
# (top) we can have the inner entrance and exit ramps have their own junction nodes with the Freewayfreeway. Do '''NOTnot''' use this approach if there are [[#Collector.2FDistributor_Lanes|Collectorcollector/Distributor Lanesdistributor lanes]] (or a similar situation) involved.# (bottom) we can have the entrance and exit ramps share a single junction node with the Freewayfreeway. This allows us to eliminate the very short Freeway freeway segment that may exist between the inner entrance and exit ramps.<br />It is best to offset this shared junction onto the Entrance entrance ramp side of the surface street. This prevents the junction from accidentally being connected to the surface street or looking like it does. We favor the Entrance entrance ramp side, because this would result in a slightly earlier exit instruction which is , of course , preferred over a late exit instruction. Use turn instruction overrides from the entrance ramp to give no instruction to the freeway and an exit instruction to the exit.
The determining factor of which design to use will partly depend on the actual size and scale of the specific interchange and if there is a [[#Collector.2FDistributor_Lanes|Collectorcollector/Distributordistributor]] involved.
'''Note on Elevationelevation:'''The single surface street segment between the inner most ramps should be either raised or lowered in relation to the freeway segments depending on the actual geography at the interchange.
=== {{anchor|Folded diamond interchange }}Folded diamond ===
: [[Image:Jct_folded_diamond.png]]
''See also: Discussion of Folded Diamonds and A2/B2 Partial Cloverleafs on the [http[wikipedia://en.wikipedia.org/wiki/Partial_cloverleaf_interchange |Partial Cloverleaf Interchange article on Wikipedia]]''
Geography or property ownership may prevent the ability for an interchange to be constructed with all ramps evenly distributed across the 4 quadrants of the interchange. When only two quadrants are used, it is typically called a Folded Diamond folded diamond (basically a sub-type of a Partial Cloverleaf Interchangepartial cloverleaf interchange). The ramps may be all on one side (as in the examples in this section) or they may be located in diagonally opposed quadrants.
The unique situation presented by the Folded Diamond folded diamond arrangement is having both Entrance entrance and Exit exit ramps terminating on the same side of the surface street. Ideally both ramps should terminate on the same junction node to permit us to easily restrict easy restriction of the illegal and usually impossible ramp-to-ramp movement.
: [[Image:Jct_folded_diamond_u-turn.png]]'
Like with a basic Diamond Interchangediamond interchange, often it will be necessary to represent the ramps making multiple connections to the surface street. Be sure to read the article [[Junction_Style_Guide#How_complex_should_ramps_be?Simple_is_better|How complex should ramps be?Simple is better]] section in the Junction Style Guide.
Restrict all non-permitted turns.
: [[Image:Jct_folded_diamond_off_turns_L.png]] [[Image:Jct_folded_diamond_off_turns_R.png]] [[Image:Jct_folded_diamond_on_turns.png]]
'''Note on Elevationelevation:''' Similar to a basic Diamond diamond interchange, in most cases only the segment of the surface street that crosses the Freeway segments will need to be adjusted up or down.
=== Single-point urban interchange (SPUI) ===
: [[ImageFile:Jct_SPUISPUI.pngPNG|750px]]''See also: [http[wikipedia://en.wikipedia.org/wiki/Single-point_urban_interchange |Single Point Urban Interchange article on Wikipedia]]''
A SPUI is a very space and flow efficient design, but it takes extra attention to ensure the turns are correct. And as the name indicates, ideally there should be a single junction in the center. You may need to tweak the geometry of segments a bit off of alignment from the real physical world, but it should be minor if the interchange is a true SPUI.
The outer branches of the exit ramps are very much like in the case of similar to a diamond interchangeand ramp to ramp routing should be enabled if possible and legal. However, in many SPUIs such ramp to ramp routing is not possible:
: [[ImageFile:Jct_SPUI_off_outer_turnSPUI outer branch.pngPNG|500px]]
Where things get complicated is the inner branches leading to the Single Pointsingle point. You need to avoid ramp-to-ramp in two directions and a reverse flow turn. '''Note:''' The ramp-to-ramp motion to facilitate a U-Turn turn (the top left arrow in the image below) may or may not be allowed depending on the specific interchange. Please validate this turn.
: [[ImageFile:Jct_SPUI_off_inner_turnSPUI inner branch.pngPNG|700px]]
Luckily the entrance ramp restrictions are similar to the diamond interchange:
: [[ImageFile:Jct_SPUI_on_turnSPUI middle branch.pngPNG|400px]]
If you were to look at all the restricted turns at once, you may get the false impression that something is very wrong. But as you now know, a SPUI has almost as many restricted turns as allowed ones.
: [[ImageFile:Jct_SPUI_all_turnsSPUI disabled turns.pngPNG|300px]]
'''Note on Elevation:'''The two surface street segments (between the outer ramps and connected to the Single Pointsingle point) and the 4 four ramp segments connected to the single point should all be the same level, either one higher or one lower than the elevation of the freeway segments above/below the single point.
=== {{Anchor|Collector/Distributor Lanes}}Collector/distributor lanes ===
These are lanes parallel to, but physically separated from, the lanes of a Freeway that serve to keep merging traffic out of the flow of through traffic on the mainline Freewayfreeway.
Collector/distributor lanes serve as either:
==== {{anchor|Collector/distributor interchanges }}Collector/distributor interchange ====
Some interchange configurations make use of collector/distributor lanes to separate lower-speed merging traffic from high-speed through traffic. This is often used in cloverleaf interchanges and in groups of nearby exits.
[[Image:Jct_fc_cloverleaf_bad.png]]
The [[Detour Prevention Mechanisms|detour prevention mechanism]] will prevent discourage Waze from routing users onto the collector-distributor and back onto the freeway – as long as the city street name on the freeway is the same (or set to "no city") before, throughout, and after the collector-distributor. Previously this feature was not available and the ramps were set up to restrict the through route. Some of these ramp configurations may still be set up that way, so they can now be configured as pictured above with the through route enabled.
==== {{anchor|Complex collector/distributor interchanges }}Complex collector/distributor interchange ====
[[Image:Collector-distributor-exit.png|thumb|right|450px|Collector-distributor lanes used in an interchange on I-81 in Christiansburg, Virginia (Exits 118A-B-C)]]
Where collector/distributor lanes are used as part of an interchange, use the {{Ramp}} type for the collector/distributor lanes. Name the ramp segments as you would any other ramp segment.
Ensure that the city a name on the Freeway segments is consistent before and after the collector/distributor lanes, so that the [[Detour Prevention Mechanisms|detour prevention mechanism]] will prevent Waze from routing users erroneously.
{{clear}}
Where collector/distributor lanes are used as part of a local-express lane configuration,
*use the same type (most likely {{Freeway}}) for the Local local lanes as is used for the Express express lanes, and*name the road as it is signed: typically "[Name] Local [Direction]": for example, "I-96 Local W" for local lanes (and "I-96 Express W" for the Express corresponding express lanes).
{{clear}}
 
=== {{Anchor|
Diverging diamond interchange (DDI)|Diverging diamond interchange|Diverging_diamond_interchange|DDI}}Diverging diamond (DDI) ===
 
''See also:'' [[Wikipedia:Diverging_diamond_interchange|Diverging Diamond Interchange]] article on Wikipedia.
[[File:DDI Example Dupont.png|thumb|845x845px|none]]
Diverging diamond interchanges (DDI) are a type of diamond interchange in which the two directions of traffic cross one another on each side of a limited-access roadway. A DDI may pass over or under the limited-access roadway.
 
This type of interchange is unusual, in that it requires traffic to briefly drive on the opposite side of the road from what is customary for the jurisdiction. However, the design of the Diverging Diamond Interchange controls the driver's line of sight to ensure the cross-over action feels natural and goes unnoticed.
 
==== Segment directionality ====
[[File:DDI Example Dupont - traffic flow.png|thumb|848x848px|Flow of traffic within a diverging diamond interchange|none]]
All ramp and surface street segments are set as one-way. If you are creating a DDI along a road which is not divided, divide the road, first. {{Details|Best map_editing_practice#Dividing_and_un-dividing_divided_highways{{!}}Best map editing practice § Dividing and un-dividing divided highways|how to properly divide/un-divide a road}}
==== At-grade intersections ====
 
===== Junctions =====
 
As with all at-grade intersections in Waze, all DDI at-grade intersections are modeled with junction nodes, ''including'' the two signaled intersections where opposing directions of traffic "cross over" each other (inner surface road junctions). A DDI may also have two outer surface road junctions, where the one-way segments transition to two-way road segments.
 
===== Turn restrictions =====
 
====== Overview ======
There are four junctions in a DDI at which the turn restrictions must be checked - two inner surface road junctions where traffic crosses, and two outer surface road junctions where the road divides/joins on each side of the DDI.[[File:DDI Example Dupont - turn restrictions.png|thumb|871x871px|All restricted turns within a DDI (displayed by using Shift+Z).|none]]
 
====== Inner surface road junctions ======
[[File:DDI Example Dupont - turn restrictions - inner - 01.png|none|thumb|871x871px]]
[[File:DDI Example Dupont - turn restrictions - outer - 02.png|none|thumb|870x870px]]Disable the ''two'' turns from one-way segments to the segments carrying traffic the ''opposite'' direction at both inner surface road intersections, for a total of four disabled turns.
 
====== Outer surface road junctions ======
[[File:DDI Example Dupont - turn restrictions - outer.png|none|thumb|871x871px]]
Disable the ''single'' turn from the one-way segment carrying traffic ''exiting'' the DDI to the one-way segment carrying traffic ''entering'' the DDI at both outer surface road intersections, for a total of two disabled turns.
== See also ==
Review the [http[Wikipedia://en.wikipedia.org/wiki/Interchange_(road) |Wikipedia article on Road road Interchanges]] for further information on this topic. {{ReturnTo | Junction_Style_Guide | the Junction Style Guide}}[[Category:Style Guides]]
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