# Difference between revisions of "Modèle:;/doc"

A somewhat simplified description of this is covered in the Junction Style Guide. Additional routing information is covered in the article How Waze calculates routes.

The description below fits a right turn in a right-hand side driving country (e.g. not England). As you may guess, Left turns are symmetrical to right turns.

## Definitions

a) s-in: the segment going into the junction
b) s-out: the segment going out of the junction
c) s1, s2 … sN: all the segments connected to the same junction
d) Best continuation - see expanded below

## What is the 'best continuation'?

In order to determine if s-out is the 'real' continuation of s-in, we do the following:
- if s-out has the same road type & street name it is selected as the real continuation.
- if not, we look at the other segments: s3, s4 … sN. One of those will be chosen as a better continuation than s-out if both following conditions are met:

• this segment has a better match street name & road type wise than s-out (e.g. it has the same street name and s-out doesn't; it has the same road type as s-in, and s-out doesn't). Street name is more important than road type.
• the angle between this segment and s-in is smaller than the angle between s-out and s-in

## The algorithm / list of conditions

The algorithm iterates over a list of conditions. As soon as a condition is met, the relevant instruction is determined, and the algorithm terminates.
The list of conditions:

1. if the junction has only 2 segments, the instruction is: 'CONTINUE'.
1.1. In some cases, T junctions could be considered as only 2 segments. See explanation on 'T junctions' below.

2. if the angle between s-out and the best continuation is larger than 45 degrees (and less than 180), the instruction is: 'TURN RIGHT'
2.1 One assumption is that on primary roads (minor highways, major highways and freeways), we won't have angles which are larger than 45 degrees.

3. if s-out is determined to be the best continuation of s-in (explanation on 'best continuation' below), the instruction is: 'CONTINUE'

4. if s-in is a primary road and s-out is not a primary road, the instruction is: 'EXIT RIGHT'

5. if s-in is a ramp/exit and s-out is neither primary nor ramp/exit, the instruction is: 'EXIT RIGHT'

6. if none of the above conditions is met, the instruction is: 'KEEP RIGHT'

## T junctions and one way roads

In some cases, a node could have more than 2 segments, but the routing server will consider only 2 of them as valid and therefore, the maneuver will be 'Continue straight'.