# Overriding Drivers

This article explains how to **override drivers** between scenarios in Model Reef.

You will learn:

* How drivers behave when each scenario is a separate model.
* Which drivers are natural levers for scenario design.
* How driver overrides cascade into many dependent variables.

Drivers are often the cleanest levers for exploring scenarios because they feed multiple variables at once.

## 1. Drivers per scenario model

Each scenario model has its own copies of all drivers:

* Economic drivers such as inflation, prices, FX and macro indices.
* Operational drivers such as units, volumes, utilisation and headcount.
* Modifier drivers such as growth rates, scenario multipliers and stress factors.

Editing a driver in one scenario does not change it in others.

## 2. Common driver overrides

Scenario modelling commonly involves changing drivers such as:

* Revenue growth or demand drivers.
* Customer acquisition or churn rate drivers.
* Price escalation or discounting drivers.
* Cost inflation or efficiency drivers.
* FX rate paths or commodity price series.
* Capacity or utilisation drivers for staff, plants or fleets.

Changing a driver can reshape many variables and branches simultaneously.

## 3. Overriding a driver in a scenario

{% stepper %}
{% step %}

### Open the scenario model

Open the scenario model you want to change.
{% endstep %}

{% step %}

### Edit the driver

Open the **Driver Editor** or the associated Data Library entry. Edit the time series, preset, forecast method or modifiers.
{% endstep %}

{% step %}

### Save

Save the changes.
{% endstep %}

{% step %}
All variables in that scenario model which reference the driver will update automatically.
{% endstep %}
{% endstepper %}

## 4. Understanding impact across the model

After changing a driver:

* Revenue, cost or other variables driven by it are recalculated.
* P\&L, Balance Sheet, Cashflow, Cash Waterfall and valuation outputs change.
* Dashboards and reports for that scenario reflect the new assumptions.

Use dashboards and comparison views to see how an override changes the overall picture relative to other scenarios.

## 5. Documenting key drivers

For clarity and governance:

* Add notes to key drivers describing their role and scenario specific values.
* Tag core scenario drivers (for example `Key scenario driver`).
* Maintain a simple list of which drivers differ by scenario when preparing board or investor material.

This helps stakeholders understand the storyline behind each scenario.

## Related articles

* [How to Enter Drivers](/syntax/how-input-fields-work/how-to-enter-drivers.md)
* [Overriding Variables](/syntax/scenario-syntax/overriding-variables.md)
* [Operational Drivers](/help/drivers-variables-and-timing/operational-drivers.md)
* [Operations & Unit Economics](/how-tos/operations-and-unit-economics.md)


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://help.modelreef.io/syntax/scenario-syntax/overriding-drivers.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.