Access state from render function

So I need to run this line of code:

var vehicles = this.state.vehicles;

In the render function:

render: function(){...}

I currently get this error:

Uncaught (in promise) TypeError: Cannot read property 'state' of undefined

Even though this line works:

this.setState({vehicles: json})

This is also part of the code:

getInitialState: function(){
    this.render = this.render.bind(this)
    return {
      vehicles: []
    }
}

How can I fix this error and access the data?