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{{ReturnTo | Junction_Style_Guide | the Junction Style Guide}}

An '''interchange''' is a road junction where two roads are connected by dedicated roadways, called '''ramps'''. The roads connected by an interchange do not intersect one another directly, and if they cross, the crossing is grade-separated.

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 Guide''' as well. The following sections discuss the proper style for ramps, interchanges, and some common 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.

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 Highways, Major Highways, and 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 and Major Highways with each other without causing problems.
* Ramp segments are relatively small but show at high 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 the beginning of a ramp, place the first [[geometry node]] of the ramp segment at the point where the solid white line begins, and extend the ramp naturally to create a junction with the road segment, typically at a 10–15° angle. This will allow for consistent timing of exit instructions.

: [[Image:Exit-ramp-geom.png]]

Do the same when placing the end of a ramp. This will allow for consistent auto-zoom functionality—the client remains zoomed in for the duration of the ramp, zooming out when the user gets on the freeway.

: [[Image:Entrance-ramp-geom.png]]

Rule #1 is still simpler is better. If there is no large distance between paths at the end of a ramp (either into or out of the ramp), a 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.

: [[Image:Jct_ramp_no_split.png]]

When paths at the end of the ramp deviate significantly in distance, regardless of the existence of any type of island, then multiple ramps should be used.

: [[Image:Jct_ramp_split.png]]

== Interchange types ==
These are junctions involving the three Highway/Freeway road types - {{Minor Highway}}, {{Major Highway}}, and {{Freeway}} -- as well as their {{Ramp|Ramps}}.

Specific examples of how to handle common junction types are provided in later sections.  All of those examples use the basic building blocks provided here.

If you are unsure what road type you should use, refer to the '''[[Road types and names]]''' for your country.

=== Exits ===
It is a basic Exit situation when a "straight" direction is obvious to a driver and navigation instructions are only needed for the non-straight direction (the exit.)  If navigation instructions are required for both directions, see the [[#Wayfinders|Wayfinders]] 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:
# The entering segment and the continuing segment must be {{Freeway}}, {{Major Highway}}, or {{Minor Highway}} type,
# The Freeway/Highway continuing segment should have close to a zero degree departure angle from the entering segment,
# The other exiting segment must be of the type {{Ramp}}, and
# The Ramp exiting segment should have a departure angle around 10–15 degrees from the entering segment, as explained above.

When those conditions are met, the navigation will present an "Exit Right/Left" instruction when the ramp is to be used, and will remain silent when the continuing Freeway/Highway segment is to be used.

==== 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/USA#Exit_ramps_and_Entrance_ramps_.28on-ramps.29|US Specific Ramp Names]]

[[United Kingdom/Roads#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.

=== {{anchor|Freeway/highway splits}} Freeway/highway forks===
A Highway/Freeway Fork  is when a Highway/Freeway segment meets at a junction with two other Highway/Freeway segments and there is no obvious straight through direction to a driver.  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 of a fork, the following must be true:
# Both exiting segments must be the same type (Freeway, Major Highway, Minor Highway).
# Each exiting segment must have a name which is different from the name of the entering segment.
# The two exiting segments should have departure angles around 10 to 15 degrees from the entering segment.

With those conditions met, the junction will present "stay to the 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 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 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 is to use named [[#Wayfinders|Wayfinder Segments]].

=== Wayfinders ===
{{Construction|draft=no|revision=yes|section=yes|contacttype=forum|contact=http://www.waze.com/forum/viewtopic.php?f=276&t=86666}}


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''' 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 right 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 to be the same road as it was before the fork. (In the following example, the lanes which continue to be I-47)

[[File:Lane definitions.png|400px|thumbnail|center]]
{{clear}}

==== Criteria (US) ====

A wayfinder is warranted in 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|right]]
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_/_keep_/_exit_maneuvers|Waze's standard rules for generating instructions]]. Please don't deviate from these precise configurations.

* Each "stub" segment should be {{: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 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 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 (either {{Freeway}}, {{Major Highway}}, {{Minor Highway}}, or {{Ramp}}, as explained below).
* Each OUT segment must have a name 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 the information displayed on the roadway signs.
** However, if this would leave an OUT segment with the same name as the IN segment, the OUT segment should be left unnamed (i.e., check the "no 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 is known, to the OUT segment name.
#Remove the compass cardinal from the OUT segment name.
#Add a space to the end of the OUT segment name (note that this will be flagged by 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 name.
#*'''NOTE:''' This option should only be used as a last resort because it prevents the [[Routing_server|routing server]] from properly calculating [[Turn delays|turn delays]], and may result in inefficient routing through the area.

If you see any of these set-ups, please correct it to one of the two proper methods listed above.}}

If the continuation is '''signed''', and a wayfinder is warranted,
* If the continuation sign contains the name or shield of the continuing road, do '''not''' use "to" at the beginning of the name of the OUT 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 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,
* [[File:Wayfinder To BGS.png|300px|thumbnail|right]]Move the shields or names affected by the "TO" to the end of the segment name after a slash (/). (The example BGS shown is for the continuation of I-80, which leads to I-280, with a control city Morristown.)
** If any included control cities or road names correlate only to the roads affected by the "TO", then those control cities or road names should be moved after the "/ to [road(s)] /" on the segment name.
*** [[File:Wayfinder To WME.png|300px|thumbnail|right]] If Morristown is served by I-80, the continuation segment should be named '''"I-80 / Morristown / to I-280"'''.
** 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-280 and ''not'' by I-80, the continuation segment should be '''"I-80 / to I-280 / Morristown"'''.{{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 US-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 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_(USA)#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 ===
A ramp may itself fork 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 fork geometry ====
: [[Image:Jct_ramp_ramp_split.png]]

==== Ramp fork naming ====
If ramps are unnamed, the name of a subsequent ramp will propagate backwards.  In the example above, if the two ramps exiting the junction are named, the ramp entering the 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 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
* Keep Left to Destination Left

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 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 B
Result: 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 St
Result: 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 B
Result: 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.

== Interchange configurations ==
Please see the [[Limited_Access_Interchange_Style_Guide|Limited Access Interchange Style Guide]].

=== Diamond interchange ===
: [[Image:Jct_diamond.png]]
''See also: [http://en.wikipedia.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.

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 onto the entrance ramp on the other side of the road should typically be enabled if legal to drive. The Big Detour Prevention Mechanism should discourage the routing server from routing someone off the freeway just to get back on it.  However, routing from ramp to ramp may be provided when freeway segment between the ramps is closed or extremely slow. Be aware that the Big Detour Prevention Mechanism is intended to prevent 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 be the same as as one name (primary or alternate) of the freeway/highway segment after the entrance ramp for the detour prevention routing penalty to be triggered.  For further information see the [[Detour Prevention Mechanisms|Big 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 [[Junction Style Guide#How complex should ramps be?|How complex should ramps be?]] 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_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 elevations:'''
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.

=== Cloverleaf interchange ===
: [[Image:Jct_cloverleaf.png]]

''See also: [http://en.wikipedia.org/wiki/Cloverleaf_interchange Cloverleaf Interchange article on Wikipedia]''

In a Cloverleaf Interchange, left turns are eliminated from all movements between the Freeway and the surface street. First check the exit ramps.

: [[Image:Jct_cloverleaf_off_outer_turns.png]] [[Image:Jct_cloverleaf_off_inner_turns.png]]

Then check the entrance ramps for illegal turns.

: [[Image:Jct_cloverleaf_on_turns.png]]

The connections to the 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 Freeway. Do '''NOT''' use this approach if there are [[#Collector.2FDistributor_Lanes|Collector/Distributor Lanes]] (or a similar situation) involved.
# (bottom) we can have the entrance and exit ramps share a single junction node with the Freeway. This allows us to eliminate the very short Freeway segment that may exist between the inner entrance and exit ramps.<br />It is best to offset this shared junction onto the 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 ramp side, because this would result in a slightly earlier exit instruction which is, of course, preferred over a late exit instruction. 

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|Collector/Distributor]] involved.

'''Note on Elevation:'''
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.

=== Folded diamond interchange ===
: [[Image:Jct_folded_diamond.png]]
''See also: Discussion of Folded Diamonds and A2/B2 Partial Cloverleafs on the [http://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 (basically a sub-type of a Partial 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 arrangement is having both Entrance and 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 the illegal and usually impossible ramp-to-ramp movement.

: [[Image:Jct_folded_diamond_u-turn.png]]'

Like with a basic Diamond 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]] 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 Elevation:''' Similar to a basic 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) ===
: [[Image:Jct_SPUI.png]]
''See also: [http://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 a diamond interchange:

: [[Image:Jct_SPUI_off_outer_turn.png]]

Where things get complicated is the inner branches leading to the Single 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 (the top left arrow in the image below) may or may not be allowed depending on the specific interchange.  Please validate this turn.

: [[Image:Jct_SPUI_off_inner_turn.png]]

Luckily the entrance ramp restrictions are similar to the diamond interchange:

: [[Image:Jct_SPUI_on_turn.png]]

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.

: [[Image:Jct_SPUI_all_turns.png]]

'''Note on Elevation:'''
The two surface street segments (between the outer ramps and connected to the Single Point) and the 4 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.

=== 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 Freeway.

Collector/distributor lanes serve as either:
* some of the ramps in an '''interchange''', or
* local lanes in configurations with '''[[wikipedia:local-express lanes|local-express lanes]]'''.


==== Collector/distributor interchanges ====

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.

===== Collector/distributor cloverleaf =====

This is a cloverleaf interchange that is connected to a collector/distributor instead of directly to the main roadway. Map collector-distributor cloverleaf ramps as you would any other ramp.

[[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. 

==== Complex collector/distributor interchanges ====

[[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 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.

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==== Local-express lanes ====

[[Image:Local-express.png|thumb|right|450px|A local-express lane configuration on I-96 in Livonia, Michigan]]

Local-express lanes are similar to collector/distributor interchange, but on a larger scale. While collector/distributor interchanges typically have an exit number or numbers, local-express lanes typically share the same name, differentiated by "Local" for the collector/distributor lanes and "Express" for the thru lanes.

A local-express lane configuration is not technically an "interchange"; however, since its physical characteristics are similar to those of a complex collector/distributor interchange, it is discussed here.

Where collector/distributor lanes are used as part of a local-express lane configuration,
*use the same type (most likely {{Freeway}}) for the Local lanes as is used for the Express lanes, and
*name the road as it is signed: typically "[Name] Local [Direction]": for example, "I-96 Local W" (and "I-96 Express W" for the Express lanes).

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== See also ==

Review the [http://en.wikipedia.org/wiki/Interchange_(road) Wikipedia article on Road Interchanges] for further information on this topic.

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