User:Nhanway/Continuity in Road Types

Continuity in Road Types

Continuity is the consistency of a road type across a routing system. For example, 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.

Imagine I have two potential routed between point A and point B:

• Route 1
  • A
  • Freeway 1
  • Road X1 (connects Highway 1 to Highway 2)
  • Major Highway 2
  • B
• Route 2
  • Freeway 11
  • Road X2 (connects Highway 11 to Highway 22)
  • Freeway 22
  • B

Both of these routes are equally valid if Road X1 and Road X2 are both Freeway or Major Highway (or even ramp, which can count as if a major highway). Waze may display either as the primary route, and will display both in the alternate routes list, assuming the trips are about the same distance and timing.

But if Short Road X1 is a Primary Street, even if it is half a block long, then Waze will not consider it a vdlia route at all, even though there is no appreciable change in time or distance, and even though it is quite short and almost the entire route is Freeway. Nevertheless, because of the pruning process for long routes, Waze will not look at any route using Road X1, and will only display Road X2.

For this reason, there are cases where a low-typed street must be "map-upgraded" as if it was a higher-typed street.

Usually, typing in the United States is based on the Waze-modified Functional Classification of roadways published by state governments. With certain exceptions, only those roads marked with special typing (arterials) will get high road typing such as Major Highway. But, sometimes it is clear that two nearby Freeways, Major Highways, or a mix of such roads, need to be connected through short segments of minor arterial roads or non-arterial roads that would normally be Minor Highway, [[Primary Street], or Street. To preserve the continuity of the highway system and allow the route to be considered, the short stretch of road may need to be up-typed to Ramp (which preserves continuity between Major Highways and Freeways), or possibly even Major Highway.

Sometimes, this is not necessary. The Functional Classification (FC) map may already acxount for this by marking a short piece of an otherwise standard road as major arterial, so that it should be Major Highway automatically. 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 groad for continuity, or leave the road at the lower designation and prevent the route. Inexperienced editors should seek help in making the decision.

Also note that continuity needs to be considered for connecting Minor Highways to other Minor Highways, Major Highways and Freeways, for loca 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 consideration:

• Can the connector road handle the volume of traffic expected for the route? I fnot, 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 interhighway 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 (FC) 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. Thats 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.

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.

So we have to make these sections of Minor Highway consistent.

Legend

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