Junction boxes History


Australia has spent years using workarounds to avoid using junction boxes (JBs), but those times must end. Many intersections around our country would benefit from a junction box, but it takes an educated and fearless editor to realise it.

This page will discuss common intersections that are important to have junction boxes in Australia. The USA wiki page has an amazing explanation of how junction boxes work and is highly recommended reading to understand the fundamentals of why junction boxes are so important to Waze.

Quickly, what’s a junction box do?

A junction box is an mechanism used by the Waze Map Editor to identify paths that a car can drive along, using only the segments within the boundary of the junction box you have drawn. A path consists of an entry, a route along multiple segments, to reach an exit. That's ultimately it.

Junction boxes create paths, which are defined by an entry, segments connected together, leading to an exit.

Why are juction box paths useful?

Improves ETAs on complex intersections

Firstly, read Turn Delays to understand how Waze calculates the transition time to drive across segments (great read, it isn't long). Then consider, when a path is defined by a junction box, Waze no longer uses the mechanism previously described, instead it utilises the time it takes to drive the path. Complex intersections are typically made up of many smaller segments and the time it takes to transition the individual segments is irrelevant. Instead, it is more useful to look at the transition time along the path, which is then used by the routing server to provide better ETAs to drivers.

Attributes can be applied to paths

  • Paths through a junction box can be disabled, similar to a turn being disabled.
  • Partial restrictions can be applied to a path (e.g. taxis only between 7-8am on Tue).
  • Custom turn instructions, such as voice prompts, visual instructions, TTS instructions, and lane guidance.

Getting the path correct

When you draw a junction box for the first time, there can be many different paths for each entry and exit combination. WME attempts to guess the best path, but it is often wrong. When adding a junction box to complex junctions, be sure to check the path for every entry/exit combination is correct. With JBs rolling out across Australia, this is by far the most common problem and disruption to routing. Consider the following example:

WME attempts to select the best route, but it is often wrong. The first path is incorrect. Use the Switch Route arrows to the select the correct path, in this case, using the turn lane.

Remember, that despite a segment turn being disabled or having restrictions, individual paths can override this or have different settings. See the below example:

To upload: Junction-box-paths-override-segment-restrictions.png


Unfortunately these amazing and powerful tools have some limitations that you should be aware of before you go designing a complex intersection that requires them:

  • Minimum lock level
  • Maximum size
    • A junction box cannot exceed 0.01° latitude and 0.01° longitude. That’s pretty massive, and you’re unlikely to reach it.
  • Minimum two junction nodes
    • A junction box must include at least two junction nodes which must be connected by a segment.
  • No overlapping
    • A junction node cannot be included in multiple junction boxes.
    • A junction node also cannot be included in a junction box path and an individually created path between two segments (paths without a junction box).
  • Maximum 16 paths
    • No more than 16 controllable entry/exit paths can pass through a single-junction node within a junction box. Adjacent connections not displayed in the routing box list are also counted.
  • Enabled u-turn on a two-way segment
    • Having u-turns enabled on a two-way segment increases the number of paths.
  • Non-navigable segments
    • Junction nodes within a junction box can't be connected to non-drivable road types unless connected by a virtual node.

Junction boxes also create new limitations that need to be considered. Once applied to an intersection, editors must delete the junction box before they can:

  • Change direction of travel (two way/one way)
  • Move a junction node across the boundary of the junction box
  • Add/delete a junction node inside the junction box
  • Add/delete/connect/disconnect a segment inside a junction box

Deleting a junction box to perform any of the above also results in the loss of all the settings attached to it - so make a note before you blindly delete any!

Where junction boxes help

H-intersection with only one allowed u-turn

There is no way to allow u-turns in one direction and not another in a H-intersection using just segment turn restrictions. The fine control of this junction box allowed paths through it to be turned on or off to meet the unique requirements of the intersection.

This type of u-turn situation is common in states like Queensland and Victoria, and is rare in other states and territories.

Control u-turns one way while allowing the other with a junction box.

Allow u-turns when median segments is less than 14m

With a median segment 14m and less, the automatic u-turn prevention mechanism kicks in and prohibits the routing server from offering a u-turn even if it is allowed by the segment turn restrictions. A junction box when applied to an intersection automatically allows all routes not prohibited by segment turn restrictions, even overriding u-turn prevention.

This type of u-turn situation is common in states like Queensland and Victoria, and is rare in other states and territories.

Intersections with smaller medians are protected by automatic u-turn prevention unless you use a junction box.

Disable u-turns when median segments is greater than 14m

With median segments greater than 14m, the automatic u-turn prevention mechanism does not apply and Waze will offer a u-turn at an intersection like the following unless a junction box is applied and the paths disabled.

This type of u-turn situation is common in states like New South Wales where u-turns at traffic lights are not allowed. Other states and territories may encounter situations where there is a combination of allowed and disallowed u-turns, which can be easily controlled with a junction box.

Intersections with larger medians are NOT protected by automatic u-turn prevention when you might expect it to. Control turns with a junction box.
If you forget to add a junction box and disable u-turns on intersections with medians larger than 14m, you're going to get some grumpy Update Requests from users.

Queued traffic through multiple junction nodes from while waiting at an intersection

Particularly during busy periods, it is important to users that Waze gives them the best route. To do this, Waze needs to understand the speed traffic is traversing segments and junction nodes. It has no understanding though that traffic queuing across multiple segments might be related unless we tell it with a junction box.

Consider the following example where the drawn vehicles are queued to turn right, meanwhile all other traffic continues zooming by heading straight. Some vehicles are moving slow on segment 2 (queued to turn right) while others move fast (going straight ahead) - Waze interprets this as traffic flow is moving fast. A junction box is needed here to tell Waze that the traffic in segment 1 and 2 are related to segment 3. Waze now treats all the segments within it as a single intersection.

In this particular example, before the junction box was added, Waze always preferred this route during peak hour. After the junction box was added, Waze now sends drivers on a faster route because it knows the traffic is slow here when turning.

Junction boxes help Waze to understand the relationship between segments by treating them as a single intersection.

Improve data collected on intricate/complex intersections

Similar to the queuing example above, Waze has no understanding that traffic queuing across multiple segments might be related unless we tell it with a junction box. A junction box over this major intersection tells Waze to treat this as one intersection instead of looking at the individual segments within it.

In the below example, following the path of the green arrow, the driver needs to cross and potentially queue across five segments (which are all allowed and legitimate). The time the driver spends on each segment is irrelevant, whereas the time to traverse the entire intersection is what Waze needs to calculate times for the best route. Also note traffic queues in six different places, and with a single junction box, the route calculation is quickly optimised for all of those paths.

It may not be obvious an intersection is complex until you examine it carefully. This junction box helped Waze understand this is one giant intersection and that the total time to travel through it is what matters, not individual segments.
An example of a complex intersection that would benefit from a junction box. How long it takes a driver to transition each individual segment inside this complex intersection isn't very useful. It is much more useful for Waze to see this as "one intersection" by adding a junction box, and understand the transitions times for specific routes through it.

Where slip/turn lanes are permitted and used correctly, and on important roads, treat them as complex intersections. This helps Waze understand that all the segments are related and that queueing traffic could occur on multiple segments.

Important intersections with slip/turn lanes used correctly are considered complex intersections that will benefit from a junction box.

Fix roundabout routing issues and override voice prompts

Launched late 2021, junction boxes can now be applied to roundabouts. This allows editors to remove several map hacks and manage paths through the roundabout and override traffic instructions easily.

In the following example, drivers were given routing instructions to follow the red path despite there being a slip/turn lane to bypass the roundabout, resulting in frequent complaints. If the turn on the roundabout was turned off at the D exit, traffic coming from A, B, and D would be unable to exit the roundabout at D. This is wrong and should never be attempted.

This is poor practice and breaks entry from all points on the roundabout.

Once a junction box is applied to the roundabout, the path travelling from C to D can been turned off, subsequently forcing C to D traffic to the slip/turn lane. Because only the path between C and D was turned off, traffic from A, B and D can still exit at D.

Junction boxes on roundabouts are new in 2021, and allow turn control on paths and voice prompt overrides.

In the roundabouts page, section understanding navigation instructions, describes how Waze automatically determines how it announces “turn left/right/continue/u-turn” or “take the first/second/third/nth exit”. Because roundabouts are sometimes different shapes or connect at different points, Waze can get the direction wrong. Using a junction box, the Voice prompt can override the default instruction, improving the Waze app experience.