User:CBenson/Routing penalties

From Wazeopedia

< User:CBenson

Revision as of 22:34, 14 March 2016 by CBenson (talk | contribs) (Up to questions about dirt road segments.)

Wazeopedia.png
This new page is currently undergoing modifications. The information presented should be considered a draft, not yet ready for use. This content is open to changes from anyone during construction. If you would like to make changes or have questions, please post a message in this forum.

The primary purpose of the Waze map is to provide a framework to present a Wazer an optimum route from one place to another place. Various street segment properties and configurations are weighted differently by the routing server. When troubleshooting routing problems it is important to understand how various segment properties configurable by a map editor effect routes provided to Wazers.

Background

Waze routing basically calculates the cost of different routes between the origin and the destination and selects the route with the least cost. When the navigation type is set to fastest the cost is primarily based on the time the route is calculated to take. When the navigation type is set to shortest the cost is primarily based on the distance of the route. The cost is based on the properties of the road segments that make up the route and the speed data collected for each road segment. There are other considerations that may cause the cost to deviate from simply the fastest or shortest route. These considerations are typically applied to the routes in the form of penalties that increase the cost of route. For example, if avoid toll road is set in the client, then the cost of road segments marked as toll is greatly increased. Thus a segment in a route that that is penalized causes the cost of the route to be higher.

Speed and Distance Data

Distance Data

Distance data is calculated based on the geometry of a segment. Thus the placement of the junction nodes at segment ends and the placement of geometry nodes within a segment change the length of a segment.

Speed Data

Speed data for a segment in a route is dependent on the next segment in the route. In this way the speed data accounts for difference in the time to make different turns (such as a right turn, continuing straight, or turning left) at an intersection. The speed data for each segment can be considered to be two components. One component is based on the time to traverse the majority of the length of the segment. The other component is based on the time waiting at the end of the segment to travel to the next segment.

  • Default Speed Data - when a road segment is added to the map it is assigned speed data based on the road type of the segment.
  • Historic Speed Data - when a Wazer drives a road segment, Waze retains the speed data from the drive. Waze retains speed data for each segment for different times of the day and for different days of the week. As speed data is collected the collected data is favored over the default speed data for the segment.
  • Realtime Speed Data - where there is speed data from Wazers that have recently driven a segment that a route will use in the near future, that speed data is used. This realtime traffic data allows waze to route around traffic jams to find the fastest route.

The editor does not control the speed data. With the exception of the default speed, the speed data is based on actual drives of Wazers. It is important for segments to be properly placed on the map in relation to the drives (as shown in the GPS layer) so that waze assigns the wazers drive speeds to the proper segment.

Client Navigation Settings

There are several options in the client application that effect how the cost of the route is calculated.

  • Navigation type - Fastest causes the route cost to be based on speed data. Shortest causes the route cost to based on distance.
  • Avoid toll road - Causes segments marked as toll to be penalized.
  • Avoid freeways - Causes freeway segments to be penalized.
  • Dirt roads - Causes dirt road segments to be penalized.
  • Vehicle type - Causes segments with appropriate vehicle restrictions to be penalized.

Segment properties

The properties of a road segment can effect routing:

  • Road Type - as mentioned above the default speed data is based on the road type. The road type also effect the routing as follows:
  • Freeway - Avoided when "Avoid freeways" is selected in the client application. When "Avoid freeways" is selected in the client application, a high penalty is applied for each freeway segment included in the route.
  • Dirt Road - Avoided based on the "Dirt roads" setting in the client. No penalty is applied when the setting is set to "Allow." A penalty is applied


The following segment properties cause routing penalties:

Road configurations

Other routing penalties are based on road configurations.

  • Ramps should prevent detour
    Waze penalizes some routes that leave a highway or freeway only to immediately return to the same freeway or highway. This is covered in more detail in Detour Prevention Mechanisms.
  • When a new node is created along a current or new segment, the node will default to a 5 second penalty through that node until someone drives across it and the map tiles are rebuilt with the new data. After that point the 5 second penalty is removed and the measured transit time through that node is used.

Preventing routes with certainty

If a segment should never be used for routing, it should not be connected to the road network. For example, Waze may route over walking trail or stairway segments connected to the road network if conditions are such that the penalized route is still found to be the best route. This is common where there are no alternate routes, such as when Waze finds that the origin or destination is on the penalized segment.