# Custom Model


A custom model allows you to modify the default routing behavior of a vehicle profile by specifying a set of rules in JSON language.
There are three JSON properties to change a profile: `priority`, `speed` and `distance_influence` that are described in great detail in the next sections and you can get a quick overview in this [example-driven blog post](https://www.graphhopper.com/blog/2020/05/31/examples-for-customizable-routing/).

But first we will give an introductory example for each of these JSON properties. Let's start with `speed`:

```json
{
  "speed": [{
    "if": "road_class == MOTORWAY",
    "limit_to": "90"
  }]
}
```

As you might have already guessed this limits the speed on motorways to 90km/h.
Changing the speed will of course change the travel time, but at the same time this makes other road classes more likely as well, so you can use this model to avoid motorways.

You can immediately try this out in the Browser [on GraphHopper Maps](https://graphhopper.com/maps/?point=50.856527%2C12.876127&point=51.02952%2C13.295603&profile=car&custom_model=%7B%22speed%22%3A%5B%7B%22if%22%3A%22road_class+=%3D+MOTORWAY%22%2C%22limit_to%22%3A%2290%22%7D%5D%7D).
GraphHopper Maps offers an interactive text editor to comfortably enter custom models.
You can open it by pressing the "custom" button. It will check the syntax of your custom model and mark errors in red. You can press
Ctrl+Space or Alt+Enter to retrieve auto-complete suggestions. Pressing Ctrl+Enter will send a routing request for the
custom model you entered. To disable the custom model you click the "custom" button again.


In the second example we show how to avoid certain road classes without changing the travel time:

```json
{
  "priority": [{
    "if": "road_class == LIVING_STREET || road_class == RESIDENTIAL || road_class == UNCLASSIFIED",
    "multiply_by": "0.1"
  }]
}
```

This example avoids certain smaller streets. [View it in GraphHopper Maps](https://graphhopper.com/maps/?point=51.125708%2C13.067915&point=51.125964%2C13.082271&profile=car&custom_model=%7B%22priority%22%3A%5B%7B%22if%22%3A%22road_class+=%3D+LIVING_STREET+%7C%7C+road_class+%3D%3D+RESIDENTIAL+%7C%7C+road_class+%3D%3D+UNCLASSIFIED%22%2C%22multiply_by%22%3A%220.1%22%7D%5D%7D).

The third example shows how to prefer shortest paths:

```json
{
  "distance_influence": 200
}
```

[View this example in GraphHopper Maps](https://graphhopper.com/maps/?point=51.04188%2C13.057766&point=51.057527%2C13.068237&profile=car&custom_model=%7B%22distance_influence%22%3A200%7D).

There is a fourth JSON property `areas` that allows you to define areas that can then be used in the `if` or `else_if` conditions for `speed` and `priority`.
Please read more about this and the other properties below and try some examples in
[GraphHopper Maps](https://graphhopper.com/maps/) with the help of
[this blog post](https://www.graphhopper.com/blog/2020/05/31/examples-for-customizable-routing/).