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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.
* 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 ===
=== 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 divide a ramp into then multiple rampsshould be used: [[Image:Jct_ramp_no_split.png]]
When paths at the end of the : [[File:Junction Style ramp deviate significantly in distance, regardless of the existence of any type of island, then multiple ramps should be usedsplit.PNG|350px]]
== {{anchor|Interchange types}}Component junction types ==Interchanges are made up of multiple individual junctions involving the following: * One or more highways, represented by the three highway road types {{Minor Highway}}, {{Major Highway}}, 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 following sections. All of those examples use these road types. If you are unsure what road type you should use, refer to the [[Image:Jct_ramp_split.pngroad types]]article.
== Interchange types ==These are junctions involving the three Highway/Freeway road types - {{Minor Highway}}, {{Major Highwayanchor|Exits}}Basic exit/entrance ===A basic exit is a junction where a single ramp exits a highway and leads to another road, and {{Freeway}} -- as well as their {{Ramp|Ramps}}the continuation of the highway is obvious to drivers. Most exits fit this description.
Specific examples of how To map a basic exit:# The entering segment and the continuing segment must be {{Freeway}}, {{Major Highway}}, or {{Minor Highway}} type and should match name and type.# The freeway/highway continuing segment should have close to handle common junction types are provided in later sectionsa zero degree departure angle from the entering segment. All # The exiting segment should be of those examples use the basic building blocks provided heretype {{Ramp}}.# The ramp geometry should be consistent with [[#Ramp geometry and complexity|ramp geometry and complexity]].
If you When those conditions are unsure what road type you should usemet and the ramp exits to the right, the navigation will present an "exit right" instruction when the ramp is to be used, refer and will remain silent when the continuing freeway/highway segment is to be used. When those conditions are met and the '''ramps exits to the left, the default instruction in the USA is "keep left." A [[road typesTurn instruction override#Exit left|turn instruction override]]''' articleshould be used to provide an "exit left" instruction at basic exits where the exit ramp departs the highway to the left.
=== Exits ===It is Similarly, a basic Exit situation when entrance is where a "straight" direction single ramp joins an existing highway, and the path of the highway is obvious to drivers. The geometry of a basic entrance junction should be mapped just like a driver and navigation instructions are only needed for the non-straight direction (the basic exit.) If navigation instructions are required for both , but with directions, see the [[#Wayfinders|Wayfinders]] section belowreversed.
==== {{anchor|Exit geometry}}Basic 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 ====The Highway/Freeway segments before and after the junction should be named the same. The ramp segments should be named in accordance with the best practices in your location. [[Road names#Exit_ramps_and_Entrance_ramps_.28on-ramps.29|US 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. === {{anchor|Freeway/highway splits|Freeway/highway forks}} Freeway/highway forksfork===A Highwayhighway/Freeway Fork freeway fork is when a Highway/Freeway segment meets at a junction with where one freeway or highway splits into two other Highway/Freeway segments , and there is no obvious straight through direction to for a driver. This can happen at the end of a concurrency of highway routes or where one or both highway routes begin. This is synonymous with the MUTCD term "split.".
==== {{anchor|Freeway split geometry}}Freeway fork geometry ====
: [[Image:Jct_fwy_fwy_split.png]]
To receive a navigation instruction for '''both''' branches Place the first geometry node of a fork, the following must be true:# Both exiting segments must be the same type (Freeway, Major Highway, Minor Highway).# Each exiting each outgoing segment must have a name which is different from at the name beginning of the entering segment.# The two exiting segments should have departure angles around 10 to 15 degrees from solid white line where the entering segment. With those conditions metroadways diverge, then move the junction will present "stay node to where each outgoing segment deviates from the incoming segment 20° right and left" and "stay to the right" navigation instructions using the name of the appropriate exiting segment
==== {{anchor|Freeway split naming}}Freeway fork naming====
The primary rule is that all 3 segments at the junction must have different names. That can be accomplished in one purpose of two ways:# Using road names alone - It is an easy situation if all three roads which connect have different names. If "Highway A" forks into "Highway B" and "Highway C", then that is all we need to have a properly functioning freeway fork.# Using signs and [[#Wayfinders|Wayfinder Segments]] - If one of the branches of the fork has the same name as the entering segment, we must create uniqueness at the junction. If "Highway X" forks off from "Highway Y" and "Highway X" continues as the other branch, the preferred approach naming is to use named [[#Wayfinders|Wayfinder Segments]]. === Wayfinders === A '''wayfinder''' gives a user an instruction directing them how to continue on the road the user is already on, in situations where it may be unclear, and there would otherwise be no instruction.  ==== Terminology ==== A '''travel lane''' is a lane which is long enough that a naïve driver might consider it a long-distance lane. For our purposes we will clarify this as any lane which;#before nearing the exit, is neither striped nor signed as a departing lane over a significant length (approximately ¾ a mile, or its full length, whichever is shorter), and#has not just started within a mile before the exit. The '''typical side''' give instructions for an exit depends on the traffic side for that country. In a country with [[Right-hand traffic]] i.e. the USA, the typical side for an exit is the both right and left side. The '''atypical side''' for an exit is the opposite of the typical side described above. A '''continuation path''' or '''continuation''' is the group of lanes after the fork which continue that are accurate to be the same road as it was before the forkposted signage. (In the following example, the lanes which continue to That can be I-47) [[File:Lane definitions.png|400px|thumbnail|center]]{{clear}} ==== Criteria ==== A wayfinder is warranted in accomplished using the following cases:*The continuation path on a controlled-access highway or freeway, when an exit is present on the typical side, has at least two fewer ''travel lanes'' after the exit than before it;*The continuation path on a controlled-access highway or freeway has the same number of lanes as, or fewer lanes than, the exit path after the fork;*The continuation path on an uncontrolled highway, or when an exit is present on the atypical side of a controlled-access highway or freeway, has at least one fewer ''travel lane'' after the exit than before it;*The continuation path consists of a single lane; or*Other conditions exist that may suggest a fork, rather than an exit (use your better judgement, and discretion) -- for example:**The physical roadway itself forks or diverges with no clear straight-ahead direction;**The road which appears to be straight ahead is not the actual continuation;**Signage and striping do not clearly provide all expected "exit" indications, or do so inconsistently; or**# Signs are present with arrows pointing left and right but no sign clearly establishes the continuation.  {{NeedImage| Need sample images for "lane drops" and "non-obvious continuations"; also, example of BGS with lane arrows}} [[File:FreewayS-inS-out.png|200px|rightwayfinder]]In these cases, we need to use a wayfinder configuration. Each wayfinder configuration will have one "IN" segment and two "OUT" segments. ==== Configuration ==== These configurations have been designed based on a very in-depth understanding of [[How_Waze_determines_turn_<nowiki/_keep_/_exit_maneuvers|Waze's standard rules for generating instructions]]. Please don't deviate from these precise configurations. * Each "> stub" segment should be {{segments:Segment length/Minimum}} long. This is long enough so it will not cause routing problems, but it is short enough to suppress display of the names (on Freeway stubs) and keep freeways looking contiguous (on Ramp stubs).* The OUT segments should have a ''turn angle'' of 10°-20° off of the mid-line on opposite sides of each other, consistent with [[Junction_Style_Guide/Interchanges#Freeway_split_geometry|the geometry for freeway forks]]. This will allow for easy identification in WME, but still look seamless in the client app.  To configure the wayfinder, * If the numbered/signed exit is on the '''right''', the OUT segments should be {{Ramp}} type. This will give an "exit right" instruction for the exit and a "stay to the left" instruction for the continuation. ** 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#Freeway.2Fhighway splits|freeway fork]], use a Ramp stub on both sides.* If the numbered/signed exit is on the '''left''', the OUT segments type should be the same as {{Road|style=background-color: #fbe73f;|the IN outgoing segment}}, in the following examples we will use the {{Freeway}} type. This will give "stay to the" instructions on both sides (if {{Ramp}} segments were used, Waze would give has a confusing "exit right" instruction for the continuation).** For a basic [[Junction Style Guide/Interchanges#Exits|exit]], 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 fork]], 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:RightExitRamp.png|191px]]|-| Right| Fwy fork| '''Continuation side'''<br/>{{Ramp|Named Ramp stub}} → {{Freeway|Named Fwy}}| '''Exit side'''<br/>{{Ramp|Named Ramp stub}} → {{Freeway|Named Fwy}}| [[File:RightExitSplit.png|191px]]|-| 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|189px]]|-| Left| Fwy fork| '''Exit side'''<br/>{{Freeway|Named Fwy stub}} → {{Freeway|Named Fwy}}| '''Continuation side'''<br/>{{Freeway|Named Fwy stub}} → {{Freeway|Named Fwy}}| [[File:LeftExitSplit.png|191px]]|}</div> ==== Segment naming ====Keep these basic principles in mind:* The OUT segments must both be the same type big green sign (either {{Freeway}}, {{Major Highway}}, {{Minor Highway}}, or {{Ramp}}, as explained belowBGS).* Each OUT segment must have a name above it that says something different than the IN segment.** '''NOTE:''' An unnamed segment (no-name box checked) is considered to have a blank name, and not the inherited name for these purposes. Therefore either both OUTs must be no-name, or both must have their own unique name.* OUT segments should be named with of the information displayed on the roadway signs.** However, if this would leave an OUT segment with the same name as the IN entering segment, cut the OUT segment should be left unnamed (i.e., check at the "no fork to create a stub and name" box). {{mbox|type=important|text=Previously in these situations segment naming was modified in one of the following ways {{u|''in order of preference''}}:#Add a control/destination city, if it according to what is known, to on the OUT segment namesign.#Remove the compass cardinal from If the OUT outgoing segment name.#Add a space to continues the end route designation of the OUT incoming segment , add that as an alternate name (note that this will be flagged by of the [[Community_Plugins,_Extensions_and_Tools#WME_Validator|WME Validator script]], if active, and possibly result in undoing by another editor)#Create a stub in the IN segment just before the junction with no street to preserve name.#*'''NOTE:''' This option should only be used as a last resort because it prevents the continuity for [[Routing_serverDetour Prevention Mechanisms|routing serverdetour prevention]] from properly calculating [[Turn delays|turn delays]], and may result in inefficient routing through the areapurposes. If you see any of these set-ups, please correct it to one of the two proper methods listed above.}} If the continuation is BGS doesn'''signed''', and a wayfinder is warranted,* If the continuation sign contains t say anything different from the name or shield of the continuing roadhighway itself, do '''not''' use "there is no need to" at the beginning of the make a stub; simply name of the OUT outgoing segment. e.g., a freeway fork where one side is the continuation of the same freeway (the user is already on the road, not going "to" it). Most wayfinders will fit this criterion.**If the name of the continuation is included but is not listed first on the sign, move with the name of the continuing road to the beginning of the segment name. (e.g. In this wayfinder the highway you are on now, and continuing on is I-275, so the segment name should be "I-275 N / I-74 E / US-52 E / Cincinnati".)* If the continuation sign '''does not contain''' the name or shield of the continuing road, then the road name should begin with "to".  If the word "TO" is explicitly included on the continuation sign,* # A [[File:Wayfinder To BGS.png|300px|thumbnail|rightturn instruction override]]Move : If one branch is named the shields or names affected by the "TO" to the end of same as the entering segment either as a primary or alt name after , use a slash (/). (The example BGS shown is for the continuation of I-80, which leads turn instruction override to I-280, with give a control city Morristown.)** If any included control cities or road names correlate only to the roads affected by the "TOkeep left", then those control cities or road names should be moved after the "/ to [road(s)] /keep right" on instruction depending upon which direction the branch leaves the segment namefork.*** For further details on freeway fork mapping, see the [[File:Wayfinder To WME.png|300px|thumbnail|rightwayfinder]] If Morristown is served by I-280 and ''not'' by I-80, the continuation segment should be '''"I-80 / to I-280 / Morristown"'''.** If any included control cities or road names correlate to the roads '''not''' affected by the "TO", then those control cities or road names should remain in place before "/ to [road(s)]".*** If Morristown is served by I-80, the continuation segment should be named '''"I-80 / Morristown / to I-280"'''page.{{clear}}
 If the continuation is '''not signed''', and a wayfinder is warranted,* If the OUT segment is a continuation of the same road, it should be left unnamed (check the "no name" box).* If the OUT segment is an exit, it should be named following the guidelines for an unsigned exit.* If the OUT segment is a short continuation of the same road leading to another road, name the segment starting with "to" followed by the name of the road to which the continuation leads, following these guidelines:** === {{anchor|no BGS to}}[[File:No BGS To exit.PNG|300px|thumbnail|right]]Where the wayfinder is just before, but not at, the termination of a road, so the continuation OUT segment is named for the road that the continuation leads to at the termination. However you still must travel for a short distance on the continuation of this road until those exits/termination. [[File:No BGS To exit zoom out.PNG|300px|thumbnail|right]]Our example here is a wayfinder on USRamp-1-9 N (Truck), the left OUT is the continuation, however the right OUT also continues on the same road until it intersects with SR-440, with an exit to SR-440 S along this short segment. There are no roadway signs for any of these ramp forks, or exits/terminations. The OUT segment here would be named '''"to SR-440 S / Communipaw Ave"''', and the SR-440 exit will be named following the [[Road_names#Exit_ramps_and_entrance_ramps_.28on-ramps.29|unsigned exit guidelines]]. However it may be appropriate (if there are no House Numbers, or other on ramps past this wayfinder before it reaches the exit, to leave this entire portion with no name, and the instruction will inherit the name of the next road to which you are going.{{clear}}  Wayfinder naming examples<div style="font-size:smaller">{| class="wikitable" style="text-align:center"|-! #! Continuation sign! Continuing road name! Rule! Waze road name|-| colspan="3" | [[File:Wayfinder I-10 BGS.png|225px|thumbnail|center]]| [[File:Wayfinder I-10 WME.png|225px|thumbnail|center]]| context image|-| 1| I-10 E / New Orleans Business District| I-10 E| Matches - do not use "to"| '''I-10 E / New Orleans Business District'''|-! #! Continuation sign! Continuing road name! Rule! Waze road name|-| colspan="3" | [[File:Wayfinder continuation TO I-71.png|225px|thumbnail|center]]| [[File:Wayfinder 471 close.png|225px|thumbnail|center]]| [[File:Wayfinder 471 context.png|225px|thumbnail|center]]|-| 2| I-71 N / Columbus| I-471 N| Does not match – use "to"| '''to I-71 N / Columbus'''|-! #! Continuation sign! Continuing road name! Rule! Waze road name|-| colspan="3" | [[File:Wayfinder continue last BGS.png|225px|thumbnail|center]]| [[File:Wayfinder 275 closeup.png|225px|thumbnail|center]]| [[File:Wayfinder continue last WME.png|225px|thumbnail|center]]|-| 3| I-74 E / US-52 E / I-275 N / Cincinnati| I-275 N| Included but not first – move to beginning| '''I-275 N / I-74 E / US-52 E / Cincinnati'''|-! #! Continuation sign! Continuing road name! Rule! Waze road name|-| colspan="3" | BGS image| WME image| context image|-| 4|||| '''name'''|-! #! Continuation sign! Continuing road name! Rule! Waze road name|-| colspan="3" | image| image| image|-| 5|||| '''name'''|}</div> === Ramp-ramp forks fork ===A ramp may itself fork and branch into two directions. If this This is synonymous with the case, MUTCD term "Exit Rightbifurcation." and "Exit Left" will Most of the time a ramp fork should be announced mapped to give instructions to traffic going either direction. This is accomplished by using the name of ramp type for both outgoing segments and names that are different from the appropriate exiting incoming segment in all casesor turn instruction overrides where necessary.
==== Ramp fork geometry ====
[[Image: Jct_ramp_ramp_split.png]] [[Image:Jct_ramp_ramp_splitjct_cd_ramp_split.png]] Ramp forks should generally have the same geometry as [[#Freeway fork geometry|freeway forks]], except for where the ramp fork is part of a [[#Collector/distributor cloverleaf|collector/distributor interchange]] or if one side of the ramp fork is using a "continue" instruction or no instruction. In this case the ramp fork should look more like a [[#Ramp geometry and complexity|basic exit]].
==== Ramp fork naming ====
If ramps are unnamed, the name Naming of a subsequent ramp will propagate backwards. In forks should generally follow the example aboveguidelines from [[Road names#Exit|road names]], if the two ramps exiting the junction but there are named, the ramp entering multiple ways to handle all the signs present at each junction 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 ===== Using information on the junction are named "DestinationLeft" and "DestinationRight". The signs directly =====A simple way to name the ramp segments in ramp that enters the junction forks is unnamed. If you need to "Exit Right" onto name each ramp segment with full or abbreviated information shown on the unnamed rampsigns leading into it. This will provide a static set of instructions for users as they travel on each segment, regardless of what their further movements will be. If you This is especially appropriate when a single sign is present at an exit, but multiple signs with different information are headed to "DestinationLeft", navigation would tell you:* Exit Right to Destination Left* Keep Left to Destination Leftpresent farther down the road.
===== Using unnamed ramps is very useful to provide sufficient notification of an approaching decision point, as long as the names of both ramp forks are visible on signs at the start of the initial ramproad name inheritance =====[[File:RampforkMUTCD.png|thumb]]
'''Example Another way to name these ramp segments is to use name inheritance. If a ramp is unnamed ("no name" box checked), the name of good use 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. If an unnamed ramp is used at an exit and subsequent named rampsare used after the fork, drivers will only see the name of whichever side of the fork they need to 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 form 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. The ramp that goes to I-17 southbound would be named "Exit 36: I-17 S / Portland" and the ramp that goes to I-17 northbound would be named "Exit 36: I-17 N / Miami." This would produce the following instructions:'''* Initial Traffic heading south on I-17 would receive*# at the exit: exit right to Exit Sign36: I-17 S / Portland*# at the fork: keep right to City A and City BExit 36: I-17 S / Portland* Traffic heading north on I-17 would receive* Destination Left Sign# at the exit: exit right to City AExit 36: I-17 N / Miami* Destination Right Sign# at the fork: keep left to City BExit 36: I-17 N / MiamiResult: An unnamed initial Note that even though the exit number is by design not shown on signs at the ramp will provide accurate and informative navigation fork, it should be included in the names of the ramps for proper instructions to at the exit. If signs at the ramp fork differ more significantly from signs at the driverexit, a different method of naming should be used.
'''Example of poor use of unnamed ramps:'''* Initial Exit Sign: to Downtown* Destination Left Sign: to Downtown====== Name inheritance, but signage on consecutive signs are different ======* Destination Right Sign[[File: 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 namedPseudoWF.png|thumb]]
If separate or split signs exist for traffic at an exit, but the signs at the ramp fork differ significantly from them, such as being further split or showing additional route numbers or control cities, the following method can be used:# Leave the exit ramp unnamed# At the ramp fork create a turn instruction override for no instruction going into a stub ramp segment of {{:Segment length/Minimum}}# Name the stub according to the sign at the ''exit''Example # At the junction of modified use of unnamed ramps:the stub with the next ramp segment create a turn instruction override to match the expected instruction at the ramp fork, either keep left or right# Name the next ramp segment according to the sign at the ''ramp fork''or leave it unnamed to inherit farther ramp namesBecause of name inheritance, the shortness of the stub, and the combination of turn instruction overrides, the name of the stub will be used in instructions at the exit, and the name of the ramp past the stub will be used at the ramp fork. This method should only be used when it's not possible to replicate what drivers see on guide signs using simple naming or name inheritance.
* 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 point.== {{Anchor|Interchange configurations}}Configurations ==
== Interchange configurations ={{anchor|Diamond interchange}}Diamond ===: [[File:Diamond interchange.PNG|750px]]''See also: [[Wikipedia:Diamond_interchange|Diamond interchange article on Wikipedia]]''
 === Diamond interchange ===: [[Image:Jct_diamond.png]]''See also: [[Wikipedia:Diamond_interchange|Diamond Interchange article on Wikipedia]]'' Common in wide open spaces where land acquisition and geography are not concerns, this Interchange interchange design has ramps equally distributed across all 4 quadrants.
In the simplest form, this can be represented as single connections from the ramps to the surface street.
The straight through motion from the exit ramp to the entrance ramp should typically be enabled, if legal to drive. Under normal circumstances, the Big Detour Prevention 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.
Be aware that the Big Detour Prevention 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 [[Detour Prevention Mechanisms|Big Detour Prevention Mechanismbig detour prevention mechanism]] page.
:[[Image:Jct_diamond_simple_turns_new.png]]
If the ramps connect to the surface street at multiple points, restrict turns which should use another ramp. Review the section on [[Junction Style Guide/InterchangesInterchange#Ramp geometry and complexity|ramp geometry and complexity]] for more details on this topic.
First we see the turns that must be restricted for the exit 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: [[wikipedia: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 [[wikipedia: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#Simple_is_better|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: [[wikipedia:Single-point_urban_interchange|Single Point Urban Interchange article on Wikipedia]]''
The outer branches of the exit ramps are similar to a diamond interchange and 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 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 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.
==== Segment directionality ====
[[File:DDI Example Dupont - traffic flow.png|thumb|848x848px|Flow of traffic within a Diverging Diamond Interchangediverging 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 ====
== See also ==
Review the [[Wikipedia:Interchange_(road)|Wikipedia article on Road road Interchanges]] for further information on this topic.
{{ReturnTo | Junction_Style_Guide | the Junction Style Guide}}
[[Category:Style GuideGuides]]
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