Routing penalties

The Waze routing server uses a system that penalizes routes to avoid undesirable situations. Penalties are measured in extra time added to the route, on top of the calculated time that driving the route is expected to take based on historical and real-time traffic data. This extra penalty time does not affect the estimated time of arrival, so it is invisible. When multiple routes are compared, however, the penalized route may not be offered even if it is the fastest route, because the invisible extra time makes it look like it takes longer than a non-penalized slower route.

Background

Historically, Waze routing was intended to work in two very different environments at the same time. One uses map information that has been carefully corrected by a group of dedicated editors. The other uses map information that was imported from an external database with no editor corrections. To support both systems, the Waze development team decided to use a penalty-based routing system. That means the various segment and junction node properties that restrict certain directions between segments were applied as a routing penalty. For example, a soft restricted turn indicated by a red turn restriction arrow and a purple questions mark does not prohibit the turn, but rather it applies a high penalty to any route through the turn. Since this is the default state of any newly connected road, this penalty permits routing through new roads where no one has driven or edited them to give better data, where no nearby options exist with allowed turns. Hard restricted turns had an even higher penalty in the past, but as the map matured through editing, the Waze team decided to make hard restricted turns an absolute prohibition on routing.

Penalties have been used for other segment properties beyond restrictions, and it has also been used for certain road configurations. The list of penalized segment properties has grown with advances in user-configurable navigation settings. Penalized road configurations have been developed to provide a smarter routing experience for the growing user base.

Segment properties

The following segment properties cause routing penalties:

• Soft restricted turn (red arrow with a purple question mark)
• Soft allowed turn (green arrow with a purple question mark, much smaller penalty than soft restricted turns)
• Difficult turn for users with "don't allow difficult turns" or "always avoid difficult intersections" selected in the app
• Unpaved road for users with "don't allow unpaved roads" selected in the app, or when segment length exceeds 300m with "avoid long ones" selected
• Toll road for all users but much larger for users with "avoid toll roads" selected in the app
•  Freeway  for users with "avoid freeways" selected in the app
•  • • • • Ferry • • • •   for users with "avoid ferries" selected in the app
•  Parking Lot Road ,  Private Road  and  Off-road / Not maintained  (with increasing amounts, respectively) when transitioning from one of these three road types to a different road type but not when entering these three road types. This is discussed in detail in Private Installations.
•  Passageway  for all vehicle types except motorcycle

Note that avoidance of difficult turns and all unpaved roads is turned on by default for users, whereas avoidance of freeways, ferries and tolls is turned off by default.

Road configurations

Other routing penalties are based on road configurations.

U-turn

• 

  Segment too short to allow two left turns

  Waze will penalize a route (which forms a U-turn) with two left turns in less than 52.49 ft (16 m) in right-hand traffic jurisdictions or with two right turns in less than 52.49 ft (16 m) in left-hand traffic jurisdictions. The specific details on configuration, and criteria for this penalty are documented in the Intersections page of the Junction Style Guide.

Detour

• 

  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.

Preventing routes with certainty

The following conditions prevent routing and do not involve penalties:

• Closure
• Hard turn restriction
• Time-based turn restriction (depending on whether conditions are met)
• Time-based segment restriction (depending on whether conditions are met)
• Non-drivable road types
• Wrong way of a one-way road
• Disconnection of one road from another
• Deletion of a road

In the past, many of these conditions created penalties and could not prevent routing with certainty, so disconnection and deletion were necessary. This table explains the various uses and trade-offs of routing prevention methods.