User:Nhanway/Continuity in Road Types

From Wazeopedia

Continuity in Waze refers to a principle of choosing specific road types to create connections between more-important road types. This is done because, for certain routes, Waze may only consider roads that are at least Major Highway, and would prune all lower road types from consideration. Thus, for a certain Major Highway to be considered for one portion of the route, it must be able to connect to other Major Highways and Freeways without having to go through a lower road type.

Consider two hypothetical routes between point A and point B. These two routes are exactly the same distance, with very similar timings. The total distance travelled in either route is
a long route
  • Route 1
    • A
    • Freeway 101
    • Road X1 (connects 101 to 102)
    • Major Highway 102
    • B
  • Route 2
    • A
    • Freeway 201
    • Road X2 (connects 201 to 202)
    • Freeway 202
    • B
Add visual of the two routes.

Suppose that route 1 and route 2 are exactly the same distance, and have very similar timings.

If road X1 and road X2 both belong to the higher-routing priority road types of freeway, major highway, or ramp, then Waze will consider them both among the alternate routes, and choose one or the other as first choice depending on the current traffic conditions.

But if road X2 has a higher-priority road types, but X1 has a lower-priority road type, such as Primary Street, Waze will reject routes that uses road X1. This is because, on long routes, a Waze avoids routing from high-priority roads like freeways to low-priority roads and back again. Even if the distance travelled on road X1 is short, and even if route 1 takes significantly less time than route 2, because of the pruning process for long routes, Waze will not consider the route involving road X1, and will only display route 2. The only way to get Waze to consider route 1 as an option for wazers is to choose a higher-priority type for road X1.

Usually, typing in the United States is based on the Waze-modified Functional Classification (FC) of roadways published by state governments. In general, Waze editors trust the state-assigned classifications and use them to decide which roads should be marked for high routing priority (major highway or freeway). But sometimes it is clear that routes between nearby high-priority roadways need to be connected through short segments of connecting roads, which the state's might have classified as minor arterial roads or non-arterial roads (Waze types Minor Highway, Primary Street, or Street). But since this dis-continuity prevents Waze from considering what might turn out to be the fastest route, Waze Mao editors need to apply the continuity principle. Depending on the road types and the physical configuration of the connector, road type of ramp or Major Highway is chosen.

Sometimes, the state FC map already accounts for this by marking a short piece of an otherwise lower-priority road as major arterial, which indicates so that it should be Waze Major Highway. But where the map is unclear about whether the highways are connected this way, or where the FC map does not show the connection at all, the editor must use judgement in deciding whether to upgrade the road for continuity, or leave the road at the lower designation and prevent the route. If you have not already done extensive testing of this type of routing issue, seek help from more experienced editors.

Also note that continuity needs to be considered for connecting Minor Highways to other Minor Highways, Major Highways and Freeways, for local routing or commute-length trips. It may also apply to continuity in Primary Streets. However, the need is usually more acute for longer trips that use Major Highway and Freeway.

Some considerations:

  • Can the connector road handle the volume of traffic expected for the route? If not, it will create a bottleneck, and may not provide a good route. Waze will eventually learn this, and not consider the route despite the continuity upgrade. But until Waze learns this, you may cause incorrect routing, and after you do it, you are causing the routing engine to work harder in calculating the route.
  • Is the nature of the street conducive to highway routing? If any part of the route looks like a quiet residential street that happens to run close to two highways, perhaps residents and traffic engineers didn't want highway traffic routing through, and the street was purposely left off the FC map.
  • How long is the route? For a short street-type segment, traffic engineers may have elected not to bother with direct ramps. For longer connections, perhaps the length of the route makes it unsuitable for inter-highway traffic.
  • Are there traffic control devices that will slow the trip? More than 1-2 stop signs, traffic lights, or turns have significant traffic-calming effects, and may significantly bottleneck the route (again, until Waze learns the route properties).
  • Is there a dearth of routing options between two regions? When you eyeball a map between two cities, does it become obvious to you that there are not enough direct routes? Do we need to find a way to tie multiple highways together to create additional routes? Do these highways have natural connections, or is Waze going to be forced to take long, out of the way extra trips down one of the highways to find a connection to another? If you find that Waze in actuality forces roundabout highway routes between two locations, and you see a way to build a non-obvious connection between the two, then consider "upgrading" the connector's Waze functional class to enable the additional route(s).

It is very important to have continuity when interpreting Functional Classification maps and picking Road Types. Part of the criteria for making FC maps is continuity, but this does not always translate into Waze flawlessly. It is also important to have continuity when picking road types in general. That's what this section is all about.

Here is an example of how the FC map does not have continuity. If we translate this directly into Waze using Road Types USA's guidelines it looks like this. This means, if traveling on one of the two  Minor Highway  the routing server could possibly not consider this this when trying to get to the  Freeway . So we have to make these sections of  Minor Highway  consistent.

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Here is an example of how the FC map does not have continuity.
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If we translate this directly into waze using Road Types USA's guidelines it looks like this.
Error creating thumbnail: Unable to save thumbnail to destination
So we have to make these sections of Minor Highway consistent.

 Fw   Freeway 
 Major   Major Highway 
 Minor   Minor Highway 
 PS   Primary Street 
 Street   Street